But I've changed! But I've changed!

Using present perfect tense clarifies that the change is relevant to the present (you're still in the state that results from the change) If you use simple paste tense, it is open-ended and can mean that this is all entirely in the past and you reverted back to binging McDonald's, etc

Sometimes we need to take bold actions to change our lifeves. Sometimes we need to take bold actions to change our lives.

Fear and doubt will be in our way,; they help us cut through the challenges. Fear and doubt will be in our way; they help us cut through challenges.

This wording is contradictory... Fear and doubt are obstacles but also helpful?? Perhaps you meant something like "We will encounter fear and doubt on our way." "In the/our way" means that something is blocking your path, metaphorically or literally

I'm not saying that to brag or flex about my new role in the company. I'm not saying that to brag or flex about my new role in the company.

ThaIt's a huge challenge, but I'll win! It's a huge challenge, but I'll win!

I wrote it just to train myself on [some] new vocabulary! I wrote it just to train myself on [some] new vocabulary!

or "practice some new vocabulary"

Yesterday I agreed to undertake a new role inat my job. Yesterday I agreed to undertake a new role at my job.

But as far as my new function wenttask goes, I think thait will be easy, because I've already did thatone it before . But as far as my new task goes, I think it will be easy, because I've already done it before .

"function" is used more for technical stuff, like in "bodily function," or for the role of concepts (ie. "Religion functions in society as a way to build communities"), and the capabilities of items/products ("Older car stereos have a function to play cassette tapes")

If somebody gaverequested (it of me |that requestI do it), I would know how to execute it. If somebody requested (it of me|that I do it), I would know how to execute it.

Since you never talked about a specific request previously, it sounds weird to say "that request". Honestly, it's kinda hard to word since you don't expand on what exactly the new role is.

It's a good increase in work. It's a good increase in work.

Sometimes I used to borrowed money onfrom the bank, and it was terrible. Sometimes I used to borrow money from the bank, and it was terrible.

"Sometimes" implies something happens habitually, so putting something like "used to" to make it pretérito imperfeito sounds a bit better. Alternatively, you could say "I borrowed money from the bank a few times" if it wasn't habitual

I used to spend a lot of money withon useless things. I used to spend a lot of money on useless things.

When I needed to picked up my wife infrom her job, I always went to McDonald's, I binged McDonald's sometimes. When I needed to pick up my wife from her job, I always went to McDonald's, I binged McDonald's sometimes.

There's a comma splice, but it's okay in casual writing

I started to ground myself in discipline, driving and built confidence in mebuilding confidence in and driving myself! I started to ground myself in discipline, building confidence in and driving myself!

This word order is better to make it clear that "myself" is the object of "driving" (this definition of "drive" requires an object)

Whether I like or not, change comes! Whether I like or not, change comes!

As you can probably tell, I went down the same path as somebody you know (maybe). As you can probably tell, I went down the same path as somebody you know (maybe).

Grammatically correct, but a strange thing to say unless you personally know the reader and are talking about someone specific they know