Learn Hardcore Japanese: kyou ha sukosi tukarete iru keredo,「koko made benkyou site oite yokatta」 to syourai no zibun ga omoeru you ni, nikki ni mizikai kansou dake kaite kara nemasu. - I’m a bit tired today, but so that my future self can think, “I’m glad I studied this much,” I’ll write just a short reflection in my diary and then go to sleep.

Using が (今日が) would be strange here, because が usually marks the grammatical subject (often in contrast to something else). Today is not the subject doing an action; it’s just the setting. So 今日は is the natural choice.

What nuance does 少し have here? Could I use ちょっと instead?

Both 少し and ちょっと can mean “a little / a bit.”

少し feels a bit more neutral or slightly formal/polite.
ちょっと is very common in casual speech and can sound softer or more colloquial.

In this sentence, which ends in polite form (寝ます), 少し matches the somewhat neutral–polite tone nicely.

You could say 今日はちょっと疲れているけれど… and it would still be natural, just a little more casual in feeling.

Why is it 疲れている and not 疲れた or 疲れています?

疲れている is 疲れる (to get tired) in the ている form, which often expresses a current state resulting from an action.

疲れた literally means “(I) got tired” or “became tired.”
- In conversation it can also mean “I’m tired,” but it focuses more on the event of becoming tired.
疲れている focuses on the ongoing state: “am (in a state of) tiredness.”

So 少し疲れている emphasizes “I’m (currently) a bit tired” as a condition.

As for 疲れています: that’s just the polite form of 疲れている. In this sentence, the tired-part is a subordinate clause (少し疲れているけれど…), and it’s very common and natural in Japanese to use the plain form there, even when the main clause ends politely (寝ます). You could say 少し疲れていますが、…寝ます, but the given version is very natural.

How is けれど functioning in this sentence? Is something missing after it?

けれど (like けど, けれども) means “although / but / even though.”

Here, it connects two parts:

少し疲れているけれど、
“I’m a bit tired, but …”
(still, I’ll do the following) 日記に短い感想だけ書いてから寝ます。

Nothing is “missing”; it’s linking the “I’m tired” situation with the contrasting action “I will still write a short comment in my diary before going to bed.”

In casual speech people sometimes end with けど。 and trail off, but here it’s clearly followed by the main action.

What does 勉強しておいて mean exactly? How is it different from 勉強して or 勉強してよかった?

〜ておく (here: 勉強しておく) literally is “do X and leave it done,” and often means:

“do X in advance / prepare X ahead of time”

So 勉強しておいてよかった is like:

“I’m glad I had (already) studied (in advance).”
“I’m glad I went ahead and did this studying beforehand.”

Compare:

ここまで勉強してよかった
“I’m glad I studied this far.” (neutral)
ここまで勉強しておいてよかった
“I’m glad I had studied this far in advance / I’m glad I took the time to study this far beforehand.”

Because the speaker is imagining their future self looking back, しておいてよかった nicely captures “I’m glad I’ll have put in this preparation.”

What does ここまで add to the meaning?

ここまで means “up to here / this far / to this extent.”

In ここまで勉強しておいてよかった, it emphasizes the amount or progress:

“I’m glad I studied this much / this far.”

Compared with just 勉強しておいてよかった, adding ここまで highlights that reaching this current level or point in the study was worth it.

(For nuance: これまで also means “until now / up to this point,” but ここまで feels a bit more like “this far (on this path I’m on right now).”)

Why is the particle と used after 「ここまで勉強しておいてよかった」?

と here is the quotative particle. It marks that what comes before it is a “quote” or “thought content.”

The structure is:

「ここまで勉強しておいてよかった」
- と
  - 思える

Literally:
“My future self can think ‘It was good that I studied this far in advance’.”

In English we use that (think that something), but in Japanese you mark the quoted/clausal content with と in expressions like:

〜と言う (to say that …)
〜と思う (to think that …)
〜と思える (to be able to think/feel that …)

How should I understand 将来の自分? Why is の there?

将来の自分 literally is “future ’s self” – in natural English: “my future self.”

Breakdown:

将来 – future (usually more personal: one’s own future)
の – connects two nouns, like “of / ’s” in English
自分 – oneself / myself

So 将来の自分 = “the version of myself in the future.”

You normally need の here; 将来自分 without の is not natural.

Also, 将来 is preferred over 未来 when talking about a person’s future life; 未来 sounds more abstract or grand (“the future of humanity,” etc.).

Why is it 思える (potential form) instead of just 思う?

思える is the potential form of 思う: “to be able to think / to be able to feel.”

In this pattern:

〜と思えるように

it carries a nuance of:

“so that (someone) will be able to think/feel that …”
“so that it will be possible for (someone) to think that way …”

So:

「ここまで勉強しておいてよかった」と将来の自分が思えるように

≈ “So that my future self will be able to think ‘I’m glad I studied this much in advance’.”

It’s not about physical ability; it’s more like “so that it will naturally come to feel that way / so that I’ll be in a situation where I can honestly think that.”

Using 思う instead would sound more like:

“so that my future self thinks (definitely thinks) that…”

思える sounds a bit softer and more like a hoped-for or potential feeling.

What is ように doing in 思えるように?

ように has several uses; here it expresses purpose / aim: “so that … / in order that …”

The pattern is:

[clause in plain form] + ように, [action you will take]

In this sentence:

Purpose clause: 「ここまで勉強しておいてよかった」と将来の自分が思える
ように – “so that”
Action: 日記に短い感想だけ書いてから寝ます。

So the overall meaning is:

“I’ll write a short comment in my diary before going to bed, so that my future self will be able to think ‘I’m glad I studied this far in advance.’”

Why is it 日記に and not 日記を before 書いて?

With 書く (to write), both 〜に書く and 〜を書く exist, but they focus on different things.

〜に書く: に marks the target / surface where something is written.
- 黒板に書く – write on the blackboard
- ノートに書く – write in a notebook
- 日記に書く – write in a diary
〜を書く: を marks the direct object (the content or the text).
- 手紙を書く – write a letter
- 日記を書く – write a diary (i.e. do diary-writing)

In 日記に短い感想だけ書いてから寝ます, the speaker is emphasizing “writing (these comments) in the diary,” so 日記に (diary as the place/medium) is natural.

You could also build a different sentence like 短い日記を書いてから寝ます (“I’ll write a short diary [entry] and then go to bed”), where 日記 becomes the object and takes を.

In 短い感想だけ, what does だけ do, and where does it attach?

だけ means “only / just.”

Here:

短い感想 – “short impressions / short comments”
短い感想だけ – “only short comments,” “just a short comment or two”

だけ attaches to the whole noun phrase 短い感想. So the meaning of the object of 書いて is:

Not a long entry, not many things – just a brief impression.

It softens the action and gives a modest, limited feeling: “I’m tired, so I’ll write just a short comment (and that’s all) before sleeping.”

How does 書いてから寝ます work? What does てから mean?

〜てから means “after doing 〜, (then) …”

Pattern:

Verb-て + から + (main action)

So:

短い感想だけ書いてから寝ます。
= “(I’ll) go to bed after writing just a short comment.”

This emphasizes the sequence: first writing, then sleeping.

Compare:

書いて寝ます – “I’ll write and (then) sleep.” (just lists actions)
書いてから寝ます – “I’ll sleep only after I’ve written (first writing, then sleeping).”

The から here is “after,” not the “because” meaning you see with 〜から in other structures.

The verb 寝ます is non-past. How can it refer to something I’m going to do later (go to bed)?

Japanese basically has two tenses: past and non-past. The non-past form (寝る / 寝ます) can cover:

present actions,
future actions, and
habitual actions.

Which one it is depends on context.

In this sentence, with the context of “today” and the sequence “write in my diary and then sleep,” 寝ます is naturally understood as a future action:

“(Later today) I’ll go to bed.”

So Japanese doesn’t need a special “will sleep” form; 寝ます can mean “sleep / will sleep,” and the time meaning comes from surrounding words and context.

Is it okay that よかった inside the quotes is plain form while 寝ます at the end is polite?

Yes, that’s very natural.

The quoted part:

「ここまで勉強しておいてよかった」

is representing the inner voice of the future self – what they’d say to themselves. Inner speech and direct quotes are normally in plain form.

The main sentence, addressed to the reader (or written as a polite diary entry), ends with 寝ます, which is polite.

So you get:

Outside narration / main clause: polite (寝ます)
Inside the quotation: plain (よかった)

Mixing styles this way between the main statement and the quoted thought is standard and natural.

More generally, is it natural to mix plain forms like 疲れている with polite forms like 寝ます in one sentence?

Yes, it is, as long as the main sentence ending is consistent with the politeness level you want.

Common patterns:

Subordinate clauses (before けれど, から, ので, とき, etc.) often use plain form, even when the final verb is polite:
- 少し疲れているけれど、寝ます。
- 忙しいから、行きません。
Quoted speech or thoughts also freely use plain form, regardless of the politeness of the main clause:
- 「ここまで勉強しておいてよかった」と思えるように、〜〜寝ます。

What would feel strange is switching politeness levels in the main sentence endings in one short utterance (e.g., ending one main sentence in です/ます and the next in casual だ in a formal context).

In this example, the overall “outside” narration ends politely (寝ます), while inner parts (subordinate clauses, quoted thought) use plain forms – which is very natural.