Learn Hardcore Chinese: wǒ zhīsuǒyǐ juéde zhè jǐ tiān yālì hěn dà, shì yīnwèi zuòyè tài duō, jiéguǒ xīnqíng yìzhí bù tài hǎo. - The reason I feel a lot of pressure these days is that there’s too much homework, and as a result my mood has been not so good.

Without 是, the sentence may feel slightly less complete or less well‑balanced in more careful/written styles, though in casual speech people do sometimes omit it.

How is this different from using 因为…所以…, for example: 因为作业太多，所以我这几天压力很大?

Both patterns are correct; the difference is mainly in focus and style:

因为…所以…
- Very common, neutral, works in almost any context.
- Structure: Because C, so R (Cause first, then result).
之所以…是因为…
- Slightly more explanatory, sometimes feels a bit more formal or rhetorical.
- Structure: The reason why R is that C (Result first, then cause).
- Highlights that you are explaining a reason.

So:

因为作业太多，所以我这几天压力很大。
Because the homework is too much, I feel a lot of pressure these days.
我之所以觉得这几天压力很大，是因为作业太多。
The reason I feel so much pressure these days is that there is too much homework.

Both are fine; the original sentence simply chooses the second style.

Why is 觉得 used here instead of 认为 or 想?

These three verbs are related but not interchangeable:

觉得 – to feel, to have a subjective impression.
- Used for feelings, personal sense, both physical and emotional.
- 我觉得这几天压力很大。 – I feel a lot of pressure these days.
认为 – to consider, to hold an opinion (often more objective, formal).
- 我认为这个办法比较好。 – I consider this method relatively good.
想 – to think, to want, to miss, depending on context.
- 我想他不会来。 – I think he won’t come.
- 我想回家。 – I want to go home.

In the sentence, 压力很大 is about the speaker’s feeling of stress, so 觉得 is the most natural choice.

Why is 这几天 placed after 觉得? Could I say 我这几天觉得压力很大 instead?

Both word orders are correct, with a small nuance difference:

我觉得这几天压力很大。
- Focus: these days are stressful.
- 这几天 modifies 压力很大 (the pressure in these days is big).
我这几天觉得压力很大。
- Focus: I have been feeling stressed these days.
- 这几天 modifies 我觉得 (in these days, I feel a lot of pressure).

In actual usage, the difference is subtle, and both can usually be used interchangeably. The original chooses pattern 1.

Why do we need 很 in 压力很大? Can I just say 压力大?

很 originally means very, but in modern colloquial Chinese it also often works like a neutral linker between a subject and an adjective:

压力很大 – literally pressure very big, but often just the pressure is big.
压力大 – more clipped; can sound:
- like an emphatic statement in some contexts, or
- like a fragment rather than a full sentence.

In everyday speech:

压力很大 sounds natural and complete.
压力大 is also used, especially in short comments or headlines, but 很 makes it sound smoother and more conversational.

So 压力很大 is the safer, more natural full-sentence choice for learners.

What is the nuance of 太多 in 作业太多 compared with 作业很多?

Both mean a lot of homework, but the attitude is different:

作业很多 – there is a lot of homework (more neutral or matter‑of‑fact).
作业太多 – there is too much homework (excessive, more than acceptable).

The sentence is complaining about stress, so 太多 is appropriate: it implies that the amount of homework is unreasonably high and causes problems.

What does 结果 do in this sentence? Is it the same as 所以?

结果 here means as a result. It introduces the outcome of the previous situation:

作业太多，结果心情一直不太好。
There was too much homework, and as a result my mood has not been very good.

Comparison:

所以 – so, therefore. Neutral logical connector.
结果 – result, outcome; often carries a sense of consequence, sometimes unexpected or negative.

If you use 所以 instead:

作业太多，所以心情一直不太好。

it is still correct, but 结果 usually sounds a bit more like you are narrating a consequence (often not a good one), which fits the tone of complaining about stress and bad mood.

Does 一直 in 心情一直不太好 mean literally nonstop, 24/7?

Not strictly. 一直 can mean:

continuously, all along, from then up to now
over the whole relevant period (here: these days)

So 心情一直不太好 is better understood as:

My mood has been not so good the whole time / throughout this period.

It does not claim there was not a single good moment; it simply describes a generally sustained state over those days. This looser, general sense is very common.

Why say 不太好 instead of 不好 or 很不好 for 心情?

These three have different strengths:

不太好 – not very good, not so good
- Softens the statement; sounds natural and conversational.
不好 – not good
- Stronger and more direct; can sound blunt.
很不好 – very not good
- Sounds quite strong or dramatic; used when you want to emphasize how bad it is.

Chinese often prefers slightly softened expressions for negative emotions. 心情一直不太好 sounds natural and appropriately mild: clearly negative, but not overdramatic.

The sentence talks about the last few days. Why is there no 了 anywhere?

了 is not required just because something is in the past. It tends to mark:

completion or change of state (aspect), or
a new situation compared with before.

In this sentence, the focus is on a state over a period:

这几天压力很大 – the pressure is/has been high in these few days.
心情一直不太好 – the mood has been not so good continuously.

These feel like ongoing states within a recent time frame, so 了 is not needed. If you added 了, you would slightly change the feel, often implying a new situation or a completed event:

这几天压力大了 – the pressure has become higher (than before).

That is a different nuance from the original.

Who is the subject of 心情一直不太好? Why is 我 not repeated?

In Chinese, when the subject stays the same across adjacent clauses, it is very common to omit it in the later clauses:

我…，是因为作业太多，结果心情一直不太好。

The understood subject for 心情一直不太好 is still 我 (my mood). It would be redundant to say:

…结果我心情一直不太好。

This is not wrong, but native speakers often leave out repeated subjects when the reference is clear from context.

What exactly does 心情 mean here, and is it different from words like 情绪?

心情 refers to one’s mood or state of mind in a fairly everyday sense:

心情好 / 心情不好 – in a good / bad mood
最近心情不太好。 – My mood hasn’t been very good recently.

情绪 is closer to emotion(s) or emotional state, and can sound a bit more technical or serious, especially in contexts like psychology or behavior:

情绪不稳定 – emotionally unstable
情绪低落 – feeling low, depressed (somewhat formal)

In a casual sentence complaining about stress, 心情一直不太好 is the most natural choice.