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.

Fear and doubt will be in our way,; they help us cut through the 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 just pouring my soul into it.

More natural --> I'm just telling you what I feel.

I would like to draw attention to this part: it'especially to this: change is not easy, but it's necessary!

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

My new life

It's good to capitalise titles: My New Life

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.

But as far as my new function wentjob is going, I think that will be easy, because I have already did thatone the same job before.

This is if you previously had the same job, then moved to your previous job. If your old job was the same as the new job: "But as far as my new job is going, I think that will be easy, because I was already doing those tasks."

But as far as my new function wenttask goes, I think thait will be easy, because I've already did thatone 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 gave me thata request, I would know how to execute it.

Or: "If someone gave me a task, I would know how to do it."

If somebody gaverequested (it of me |that requestI 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 good increase inmy work.

More natural: "I'm happy to be working more."

It's a good increase in work.

Sometimes II have previously borrowed money onfrom the bank, and it was terrible.

You borrow money FROM the bank/your friend/etc

Sometimes I used to borrowed money onfrom 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.

You spend money ON things

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

When I need to picked up my wife infrom her job, I always went to McDonald's,. I used to binge McDonald's sometimes.

I put "used to" as your next sentence says you've changed.

When I needed to picked up my wife infrom 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 meyself!

You have confidence in yourself

I started to ground myself in discipline, driving and built confidence in mebuilding 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 it or not, change comehappens!

Whether I like or not, change comes!

No matter how old I get, no matter how much money I get... theevery changes starts with the first step!

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