One sStep at a tTime

In title case, the first word, last word, and any important words (like nouns and verbs) in between are capitalized.

This can be the title of a phrase that I have been followed my whole life.

You could say:

that I have followed

OR

that I have been following

I had convinced myself to getachieve my hardest goals in life with this oin mind.

"get goals" isn't a common way to say what I think you mean; you could say

pursue my hardest goals

OR

achieve my hardest goals

OR

go after my hardest goals

OR

strive toward my hardest goals

Those are just some alternatives.

And, lLet me express, that really worked!…, and it still works for me.!

In oral communication, we often start sentences with conjunctions like "and" or "but," but not as much when writing.
Also, the "..." ellipsis is usually used in the midst of a sentence, rather than after a punctuation mark.

Life has surprises and different tones in the grayscale of gray, although,, but many of the purposes and duties that I had pursued, were accomplished step by step, sometimes ahead, sometimes behind, taking and releasing, praying and making big mistakes.

It is not very common to use commas as often as here; you've made some decisions to develop your own writing voice, so we're not strictly bound to standard grammar conventions, but the commas I removed were, I believe, unnecessary and disruptive.

But, aAbove all, though, I felt grateful to have my loved ones by my side, and they are supporting me until now, holding my hand in bad times and cheering me up in good times.

If you are describing how you currently feel, this would be better:

Above all, though, I feel grateful to have my loved ones by my side, and they are supporting me still, holding my hand in bad times and cheering me up in good times.

Now, to my kids, that are now who are in a kind of hurry to getpursue their goals rapidly, I use to state, Osay, "one step at a time…."

From what I can tell, an ellipsis at the end of a quote still needs an ending punctuation mark (here, a period). Also, "are in a hurry" is in the present tense, but "use to say" or "used to say" (use to say is not correct) is in the past tense. The tense should match in this case. You can either say:

"kids who were in a hurry" ... "I used to say"

OR

"kids who are in a hurry" ... "I say"

Lastly, "state" isn't wrong, but it is rather uncommon to see it used in this informal scenario.

One sStep at a tTime

This can be the title ofis a phrase that I have been followed my whole life.

'have followed' or 'have been following'

I had convinced myself to getmanaged to reach my hardest goals in life with this oin mind.

And, let meI would like to express, that it really worked!… aAnd still works for me.

Life has surprises and different tones in the scaleshades of gray, a. Although, many of the purposes and duties that I had pursued, were accomplished step by step, s. Sometimes ahead, sometimes behind, t. Taking and releasing, praying and making big mistakes.

But, above all, I felt grateful to have my loved ones by my side, t. They arhave supportinged me until now,: holding my hand in bad times and cheering me up in good times.

Now, tTo my kids, that are now in a kind of hurry to get reach their goals rapidly, I use to, I state, O one step at a time….