Even if they are technichally not true since they are absolutes, sometimes believing in these things can have huge benefits:
You are responsible for everything that happens to you.
This belief puts you in the driver's seat of your own life. It makes you look for what you could have done better so that you can improve next time. You see this mentality in a lot of great basketball players - even if the team loses the game because another player missed a simple shot, they don't blame it on them. Instead they say "it's on me, I could have done something." I think that's a sign of a great leader.
You can do anything you set your mind to.
Believing in this makes it almost infinitely more likely that you'll be able to achieve your goals. Even if you end up failing, you will still get somewhere. As the saying goes, “Shoot for the moon. Even if you miss, you'll land among the stars.”
In the end, everything will turn out fine.
This gives you the confidence to take risks.