When I'm not motivated to do something, I remember that inind myself that I spend mostly of my free time I spend it doing useless stuff, like scrolling social media.

You can also say remember, it just slightly changes the meaning.

If I have time to do useless stuff, why I can't I use this time to do what I need to do ?

When I question it to myself, I getask myself this question, I feel motivated.

Or "Asking myself this question motivates me."

It works sometimes works.

Your sentence was correct but "It sometimes works" sounds more natural.

Another thing that gives me motivation to domotivates me to complete my tasks is to remembering that I'm not eternimmortal,. I need to do the boring tasks/stuff to make this world better for my community, for my future kids, and for those people who aren'twho haven’t been born yet.

"Complete" is better than "do" in this context. Also, "for" does not need to be repeated in this sentence structure. Just mentioning it once is enough for the sentence to flow.

When I'm not motivated to do something, I remember that in mostly of my free time I spend it doing useless stuff, like scrolling social media.

If I have time to do useless stuff, why I can't use this time to do what I need to do ?

When I question it to myselfask myself this question, I get motivated.

Another thing that gives me motivation to do my tasks is to remember that I'm not eternal, I need to do the boring tasks/stuff to make this world better for my community, for my future kids, and for those people who aren't born yet.

When I'm not motivated to do something, I remember that in mostly of my free time, I spend it doingtime useless stuff, like scrolling social media.

If I have time to do useless stuff, why I can't use thisat time to do what I need to do ?

When I question it to myselfask myself that question, I get motivated.

It works sometimes.

this sentence is correct, but you could add some flavour to it, like “it works sometimes, but not always.” or “it doesn’t always work, but sometimes it does.” the first sentence has more focus on it not working sometimes, and the second has more focus on the times that it DOES work.

How I Motivate Myself To Complete Tasks

How I motivate myself to complete tasks

When I'm not motivated to do something, I remember that during mostly of my free time I spend it doing useless stuff, like scrolling through social media.

When I question it to myself, I get motivated.

Another thing that gives me motivation to do my tasks is to remember that I'm not eternal, will not live forever and I need to do the boring tasks/stuff to make this world better for my community, for my future kids, and for those people who aren't born yet.

How I Motivate Myself Tto Complete Tasks

When I'm not feeling motivated to do something, I remember that inI spend mostly of my free time I spend it doing useless stuff, like scrolling social media.

When I question it toask myself this, I get motivated.

It works sometimeSometimes it works.

Sounds better this way round.

Another thing that gives me motivation to do my tasks is to remember that I'm not eternal, won't live forever. I need to do the boring tasks/stuff to make this world better for my community, for my future kids, and for those people who aren't born yet.

How I Motivate Myself Tto Complete Tasks

When I'm not motivated to do something, I remember that in mostly of my free time I spend it doing useless stuff, like scrolling on social media.

If I have time to do useless stuff, why I can't I use this time to do what I need to do ?

When I question it to myself, I get motivated.

Grammatically correct, but does not sound natural. Its more common to say “When I ask (the question to) myself, I get motivated.” Parenthesis can be omitted or included.

Another thing that gives me motivation to do my tasks is to remember that I'm not eternal,. I need to do the boring tasks/stuff to make this world better for my community, for my future kids, and for thosthe people who aren't born yet.

“I’m not eternal” would not be commonly said. You can say “I don’t live forever.”

You dont need “for” before future kids and people who aren’t born yet. It can be omitted since you put it before “my community.”

When I'm not motivated to do something, I remember that inI spend mostly of my free time I spend it doing useless stuff, like scrolling social media.

In order to fix a couple grammatical errors, I inverted your phrase.

If I have time to do useless stuff, why I can't I use this time to do what I need to do ?

When I question it to myself, I getmyself that question, I become more motivated.

Another thing that gives me motivationmotivates me to do my tasks is to remember that I'm not eternal,. I need to do the boring tasks/stuff to make this world better for my community, for my future kids, and for those people who aren't born yet.