Learn Hardcore Japanese: kyou ha yoyuu ga aru kara, tonikaku tanosimou. - I have some leeway today, so anyway, let’s have fun.

今日は余裕がある = As for today, there’s leeway. Using 今日が here would clash with 余裕が (double が). If you really want to emphasize “today” as the subject, you’d rephrase, e.g. 今日なら余裕がある (“if it’s today, there’s leeway”) or 今日が一番余裕がある (“today is when we have the most leeway”). But in your sentence, 今日は is the natural choice.

Why is が used with 余裕 and ある?

With existence/possession, Japanese uses the pattern “Noun + が + ある/いる.”

余裕がある = There is leeway / (I) have leeway
時間がある = There is time / (I) have time
友だちがいる = I have friends

So が marks what exists/is possessed.

Is it okay to drop が and say 余裕ある?

Casually, yes, especially in speech:

今日、余裕あるから (casual) ≈ 今日は余裕があるから (neutral) But in writing or formal speech, keep が. Also, when modifying a noun you don’t say 余裕ある人; you use 余裕のある人 (“a person who has leeway”).

What is the nuance of から here? How is it different from ので or 〜し?

から: “because/since” with a clear, direct reason. Neutral-casual to neutral-formal.
ので: “since/as,” softer and more formal/polite; often used with ます/です.
〜し: adds a reason among others (“and besides…”). Implies there are additional reasons.

Examples:

今日は余裕があるから、とにかく楽しもう。 (direct reason)
今日は余裕があるので、とにかく楽しみましょう。 (softer/polite)
今日は余裕があるし、とにかく楽しもう。 (one of several reasons)

What does とにかく mean here, and how is it different from とりあえず or ともかく?

とにかく: “in any case/anyway.” Pushes aside details and moves on.
とりあえず: “for now/for the time being (as a first step).” Suggests a provisional action; we might handle other things later. とりあえず楽しもう sounds like “Let’s just have fun for now.”
ともかく: “setting X aside.” Often used as Nはともかく (“putting N aside”). As a sentence adverb, it overlaps with とにかく but is more like “be that as it may.”

Why is it 楽しもう and not 楽しむ? What form is this?

楽しもう is the volitional form (the “let’s” form).

For godan verbs (u-verbs): change the final -u to -o + う → 楽しむ → 楽しもう, 行く → 行こう
For ichidan verbs (ru-verbs): stem + よう → 食べる → 食べよう
Irregular: する → しよう, 来る → こよう

楽しむ is the dictionary form (“to enjoy”), not a suggestion. 楽しもう = “Let’s enjoy (ourselves).”

How would I make this sentence polite?

Use the polite forms:

今日は余裕がありますから、とにかく楽しみましょう。

You can also switch から to the softer ので:

今日は余裕がありますので、とにかく楽しみましょう。

Can I say 楽しい to mean “let’s have fun”?

No. 楽しい is an adjective (“fun/enjoyable”). To suggest doing something, use:

楽しもう (casual “let’s enjoy”)
楽しみましょう (polite) Other natural options:
楽しく過ごそう／過ごしましょう (“Let’s spend our time enjoyably”)
思い切り楽しもう (“Let’s enjoy to the fullest”)

Who is the subject here? Who has the 余裕?

Japanese often omits the subject. Context plus 楽しもう (“let’s…”) implies “we.” So it effectively means “We have leeway today, so let’s have fun.” In other contexts it could mean “I.”

Can I move とにかく to the start? Does the meaning change?

Yes:

とにかく、今日は余裕があるから楽しもう。 Placing it at the start makes it a discourse marker (“Anyway,”), guiding the listener. In the original position it more directly modifies the action (“let’s just have fun, whatever else”). Both are natural.

Any pronunciation tips for the sentence?

Readings: 今日（きょう）は余裕（よゆう）があるから、とにかく楽しもう（たのしもう）.
は is pronounced “wa” here (topic particle).
The final 〜おう in 楽しもう is a long “ō” sound (tanoshimō). Don’t clip it.
No spaces are used in normal Japanese writing: 今日は余裕があるから、とにかく楽しもう。

Can I use 余裕だ instead of 余裕がある?

They overlap but aren’t identical.

余裕がある: there is spare capacity (time/money/mental space).
余裕だ: “no sweat/easy” or “it’s chill.” Often used about tasks/situations: このテストは余裕だ (“This test is a breeze”).
You might hear 今日は余裕だ colloquially to mean “Today is easy/relaxed,” but 今日は余裕がある is the neutral, clearer way to say you have leeway today.

How do I say the opposite?

Use the negative:

今日は余裕がないから、また今度。 = “I don’t have any leeway today, so let’s do it another time.”
Common collocations: 時間に余裕がない, 心の余裕がない.

Are there other natural tweaks to the sentence?

Yes, depending on tone:

More reasons: 今日は余裕があるし、とにかく楽しもう。
Softer invite: 今日は余裕があるから、楽しもうね／楽しもうか。
Emphatic/casual: 今日は余裕があるから、楽しもうぜ。
Colloquial “go ahead and enjoy”: 今日は余裕があるから、楽しんじゃおう。 (friendly, informal)