If I were asked to answer this question about an year ago, I suppose I'd say "nothing"."

Punctuation goes inside of the quotation marks.

That's because last year, I couldn't appreciate myself.

"Last year" is considered an introduction phrase, so a comma would typically follow, for clarity.

This also applies to the studying process.

Personally, I would remove the period after "process," and replace it with an em-dash (-- symbol). Em-dashes are used to separate lists and additional information. While it isn't a problem, an em-dash would just add clarity and make the sentence more readable.
It would read as: "My best friend says that I'm never not full of energy or motivation -- this also applies to the studying process."

Recently, I heard a quote like ” : "That the possibility to achieve a goal is what makes life meaningful”," which is so relatable to me.

1. A comma to separate the introduction word, "recently."
2. A colon (: symbol) to specify what the quote is.
3. Spacing and punctuation inside the quotations.

This is why I never stop to working very hard to achieve the dreams that I have set up for myself.

The present-tense conjugation of "to work" is "working."

I tend to keep my emotions under control and prefer to deal with my frustrations on my own rather than confront others.

Again, I, personally, would remove the period after "issues," and replace it with an em-dash (-- symbol).
It would read as: "I don't have to deal with anger issues -- I tend to keep my emotions under control and prefer to deal with my frustrations on my own rather than confront others."
My reasoning: it lists an example of why you don't have anger issues. It also improves the flow of reading.

And, I might lie if someone forces me to tell the truth, even though I am not comfortable with that.

The sentence is not grammatically wrong, however "and," "plus," or even "also" would do well at the start, to improve the flow of reading.

But, I love my ability beingto be straightforward, even without trying to do that.

A comma after "but," to separate the clauses / introductory word. And, a comma after "straightforward," to separate another clause.

I just don't see any point of tellsaying something I don't believe in.

Instead of focusing only on our flaws, we should also to turn attention to our positive qualities, whatich can lead us to developing into a positive direction and keeping self-confidence high.

If I were asked to answer this question about an year ago, I suppose I'd say "nothing".

However, after some reflection, I concluded that I have some positive personality qualities / personality traits, despite the fact I may not be a perfect person. / despite the fact that I may not be perfect.

I am going to talk about the three personality traits (that) I love the most about myself.

I'm quite a productive person and dedicated withto my goals. / I'm quite productive and...

This is why I never stop to work ing (very) hard to achieve the dreams that I have set up for myself.

For example, my newest goal is to be able to speak Spanish fluently, which, I'm sure, I'll achieve one day.

I don't have to deal with anger issues.

Your sentence is perfectly correct, but since you're listing personality traits, I think this way is better.

However, I can become frustrated when I feel like my personal space is threatened or someone doesn't treat me right / ...I feel like my personal space is being threatened or someone isn't treating me right.

Truthfully, I'm not always honest all withe time with peoplehe people (whom) I don't trust.

I just don't see any point of in saying/telling something I don't believe in. / I just don't see the point of .....

Such a quality is often admired and appreciated by people who surround you, because it shows that I amyou are a reliable person and Iyou respect myour own values.

The person you're talking about in the first half of the sentence is "you," so to be consistent, the person in the second half should also be "you."

Instead of focusing only on our flaws, we should also tour turn attention to/towards our positive qualities, which can lead us to developing into a positive direction and keeping our self-confidence high.