You never get used to rejection. It’s a myth, I still think about rejections I had back over the years and they bother me to this day. That’s like saying “you’ll get used to abuse eventually, just stick with it!”.
Not in my case. I have been rejected by plenty of women and it doesn't bother me in the least. I reject hundreds if not thousands of women every day, by walking by them as I go about my day and not taking the opportunity to cold approach them because I don't find them attractive. Then when I do find a woman attractive, I approach her. If she isn't interested in me, that's fine. Doesn't hurt my feelings in the least. Why would I base my sense of self-worth and value on whether or not a random female stranger is or isn't interested in going on a date with me?
It used to bother me before I understood the rational vs irrational mindset around women rejecting you. But once I realized just how ridiculous it is for me to devalue myself because a woman who doesn't even know me has said she doesn't want to go out on a date with me, that's when it no longer bothered me. If I am out of practice with cold approach because I've been in a relationship for a while, there are a small amount of nerves right before doing the approach, but once it is done, if she says she isn't interested, it literally doesn't effect me one bit.
Say a woman only likes overweight red heads and you don't fit that mold. Why on earth should you feel less about yourself because she says she isn't interested in you?! Or maybe she has a boyfriend already. Or maybe she only dates really young or really old guys and you are neither. Maybe she only likes guys of an ethnicity that you aren't. Do you really expect yourself to be attractive to every woman on the planet, and if you aren't, then you should be ashamed of yourself and think less of yourself? You see how ridiculous that mindset is?
If you have rejections that bother you to this day, that is something you should face head-on. It's not healthy.