Jīntiān wǒ de xīnqíng bú tài hǎo.

In Mandarin, time words often come near the beginning of the sentence, before the main comment.

So:

• 今天我的心情不太好。
• 我今天心情不太好。

Both are natural and mean essentially the same thing: Today, my mood is not very good.

Starting with 今天 puts immediate focus on when this is true.

Mandarin often does not use a verb like to be before an adjective.

In English, you say:

• My mood is not very good.

In Mandarin, you can simply say:

• 我的心情不太好。

Here, 好 acts as the predicate by itself. This is very common in Chinese.

So the structure is not literally my mood is not very good with a separate is. It is more like:

• my mood not very good

That is completely grammatical in Mandarin.

心情 means mood, state of mind, or how someone feels emotionally.

It is usually about your emotional condition, not a physical condition.

For example:

• 我今天心情很好。 = My mood is good today.
• 她最近心情不太好。 = Her mood has not been very good lately.

It is more specific than just heart or feelings. It usually refers to your general emotional mood at that moment or during a period of time.

的 is often used to show possession or modification.

So:

• 我 = I / me
• 我的 = my
• 我的心情 = my mood

This is the standard possessive pattern:

• 我的书 = my book
• 他的老师 = his teacher
• 我们的家 = our home

In this sentence, 我的心情 clearly means my mood.

Yes. 我心情不太好 is very natural and common in spoken Mandarin.

So both work:

• 我的心情不太好。
• 我心情不太好。

The version without 的 can sound a little more direct and conversational. The version with 的 can sound slightly more explicit or structured.

English speakers often expect possession to always be marked, but Chinese sometimes allows it to be dropped in familiar expressions like this.

不太好 is softer than 不好.

• 不好 = not good / bad
• 不太好 = not very good / not so good

So 不太好 often sounds less harsh and more natural in everyday conversation.

Compare:

• 我今天心情不好。 = My mood is bad today.
• 我今天心情不太好。 = My mood is not very good today.

The second one can sound more polite, understated, or emotionally natural.

In this sentence, 太 is part of the pattern 不太 + adjective, which means not very or not so.

So:

• 不太好 = not very good
• 不太忙 = not too busy / not very busy
• 不太舒服 = not very comfortable / not feeling very well

Be careful: 太 by itself often means too or very depending on context.

For example:

• 太好了！ = Great! / That’s wonderful!
• 太贵了。 = Too expensive.

But in 不太好, it works together with 不 to soften the adjective.

This is a tone change rule called tone sandhi.

Normally, 不 is fourth tone: bù.

But when 不 comes before another fourth-tone syllable, it changes to second tone: bú.

Here:

• 太 = tài (fourth tone)

So:

• 不太 is pronounced bú tài

This change is about pronunciation, not meaning.

Compare:

• 不好 = bù hǎo because 好 is third tone
• 不太好 = bú tài hǎo because 太 is fourth tone

Yes. 好 basically means good here.

But in Mandarin, adjectives like 好 are used very broadly. In this sentence, 好 describes the condition of 心情, so it means:

• good
• fine
• well

So 心情好 means to be in a good mood.

Yes, absolutely. That is very natural.

Common versions include:

• 今天我的心情不太好。
• 今天我心情不太好。
• 我今天心情不太好。

All are fine.

The differences are mostly about rhythm and emphasis, not basic meaning.

It is neutral and very natural. You can use it in normal conversation.

• 今天我心情不太好。 sounds like something you would really say.
• It is not especially formal.
• It is not slangy either.

If you want to sound a little more conversational, many people would say:

• 我今天心情不太好。

It mainly refers to emotional mood, not physical health.

If you want to talk about not feeling well physically, you would more likely say something like:

• 我今天不太舒服。 = I’m not feeling very well today.
• 我今天身体不太好。 = My physical condition is not very good today.

So 心情不太好 specifically points to mood or emotions.

You can replace 不太好 with 很好:

• 今天我的心情很好。 = My mood is very good today.

Or use other natural variations:

• 今天我心情不错。 = My mood is pretty good today.
• 今天我心情特别好。 = My mood is especially good today.

This sentence pattern is very useful:

• 今天 + 我 + 心情 + 很/不太 + adjective

In normal Chinese writing, this sentence is written without spaces:

• 今天我的心情不太好。

The spaced version is usually for learners, to help show the parts more clearly:

• 今天 / 我 / 的 / 心情 / 不 / 太 / 好

This can be useful for study, but native writing does not normally separate words like this.