Deep inside, no matter how many times I overcome my fears, I'm still "scared" of rejection.

It's an irrational fear, and I hate it.

feel you, anxiety is a bitch.

Then improve yourself really good so nobody can't reject you.

I disagree, fear of rejection is not irrational at all.

It's the most normal thing to be scared. Even the thoughest ones have fears.
The most important thing is, how you deal with your fears and insecurity.
A good way to try to overcome a fear is to confront it, may be in a slow appoach, but this will make a progress.