Я не могу не признать, что твой совет помог мне успокоиться.

In this pattern, the two не do produce a positive overall meaning:

• не могу = I cannot
• не признать = not admit

So literally it is I cannot not admit.

In natural English, that usually becomes:

• I have to admit
• I can’t help but admit
• I can’t deny

This is a very common Russian structure:

• не могу не согласиться = I can’t help but agree
• не могу не отметить = I have to point out / I can’t fail to note

So here Я не могу не признать means something like I have to admit.

This is about aspect.

• признать = perfective
• признавать = imperfective

Here the speaker means a single completed act: to admit / acknowledge a fact. That is why признать is natural.

So:

• Я не могу не признать... = I have to admit...
• Я не могу не признавать... would sound unusual here, because it suggests an ongoing or repeated process of admitting.

A good rule of thumb: after не могу не..., Russian often uses a perfective infinitive when talking about one definite act.

Here признать means to admit, to acknowledge, or to recognize as true.

In this sentence, it means the speaker is acknowledging a fact:

• Я не могу не признать, что твой совет помог...
• I have to admit that your advice helped...

It does not mean to confess in the strong personal sense. For that, Russian often uses признаться.

Compare:

• признать ошибку = to admit a mistake
• признаться в ошибке = to confess to a mistake

In your sentence, признать is the better verb because the speaker is acknowledging the truth of the following statement.

Because что introduces a subordinate clause:

• Я не могу не признать, что...
• I have to admit that...

In Russian, when что means that and starts a subordinate clause, a comma is normally required.

So the sentence is divided like this:

• Я не могу не признать,
• что твой совет помог мне успокоиться.

This comma is standard and necessary.

Что here means that and introduces the content of what is being admitted.

So:

• Я не могу не признать = I have to admit
• что твой совет помог мне успокоиться = that your advice helped me calm down

It connects the main clause to the statement being acknowledged.

Because твой совет is the subject of the subordinate clause:

• твой совет помог мне успокоиться
• your advice helped me calm down

The subject is in the nominative case, so you get:

• твой = nominative masculine singular
• совет = nominative masculine singular

That is why it is твой совет.

Russian past tense verbs agree with the subject in gender and number.

The subject is совет, which is:

• masculine
• singular

So the verb is:

• помог = masculine singular past tense of помочь

Compare:

• совет помог = the advice helped
• идея помогла = the idea helped
• слова помогли = the words helped

So помог matches совет.

Мне is the dative case of я.

The verb помочь / помогать usually takes the person being helped in the dative:

• помочь мне = to help me
• помочь тебе = to help you
• помочь ему = to help him

So:

• твой совет помог мне успокоиться
• literally: your advice helped to me calm down
• natural English: your advice helped me calm down

The dative marks the person who benefited from the help.

Russian often uses this pattern:

• помочь кому? + infinitive
• to help someone do something

So:

• помог мне успокоиться
• helped me calm down

Other examples:

• Он помог мне понять. = He helped me understand.
• Она помогла нам решить проблему. = She helped us solve the problem.

So the infinitive успокоиться tells you what the advice helped the speaker do.

Because успокоиться means to calm down oneself, while успокоить means to calm someone/something down.

Compare:

• успокоиться = to become calm / calm down
• успокоить кого-то = to calm someone down

In your sentence, the speaker is the one becoming calm, so the reflexive verb is needed:

• помог мне успокоиться = helped me calm down

If you said успокоить, it would imply calming someone or something else.

The ending -ся makes the verb reflexive.

With many verbs, this changes the meaning from acting on something else to the subject undergoing the change.

Here:

• успокоить = to calm someone/something
• успокоиться = to calm down

So -ся shows that the subject is, in effect, the one becoming calm.

This is very common in Russian:

• открыть = to open something
• открыться = to open
• остановить = to stop something
• остановиться = to stop

Because the sentence focuses on the result: the advice helped the speaker reach a calmer state.

• успокоиться = perfective, to calm down as a completed result
• успокаиваться = imperfective, to be calming down / to calm down repeatedly / in process

Since the idea is the advice helped me calm down, the perfective form is the natural choice.

Not quite. I admit is weaker and more neutral.

Я не могу не признать has a stronger nuance:

• I have to admit
• I can’t help but admit
• I cannot deny

It suggests that the speaker may be reluctant, or that the evidence is too strong to ignore.

So while I admit captures the basic idea, it misses some of the tone.

Yes, Russian often omits subject pronouns when they are clear from the verb form.

So you could say:

• Не могу не признать, что твой совет помог мне успокоиться.

This still clearly means I have to admit that your advice helped me calm down.

Including Я makes it a bit more explicit and can add slight emphasis or just sound fully neutral, depending on context.

Yes. Совет can mean:

• advice
• a piece of advice
• a suggestion

In this sentence, твой совет помог мне успокоиться most naturally means:

• your advice helped me calm down

English often uses uncountable advice where Russian uses singular совет.

So the Russian singular does not force you to say a piece of advice, although that can also work in some contexts.

It breaks down like this:

• Я = I
• не могу = cannot
• не признать = not admit
• что = that
• твой совет = your advice
• помог мне = helped me
• успокоиться = calm down

Very literally:

• I cannot not admit that your advice helped me calm down.

Natural English:

• I have to admit that your advice helped me calm down.
• I can’t help but admit that your advice helped me calm down.