The biggest thing that's stopping you is the belief that something is stopping you.
Every change is easier said than done. You've got now and from now, on. That's it, but that's a lot.
If your mind has been on repeat that there's no point in even trying then it's going to take some extra effort to change that thinking.
There is a point in trying and that point is to make the rest of your life better than the current course it's headed on. Even if you're tired...Nothing is more energizing than working towards something amazing, and that something amazing is your life.
Make it so.