I had a big problem with this until the end of my senior year of high school when I just started asking a bunch of girls out anyway because I knew I wasn't going to see them anymore and thus it'd be less embarrassing when they turned me down, which most of them did. But what I found was that the more I got rejected, the less I cared about getting rejected, which in turn made me more confident when I approached them because I didn't care about the outcome, and as I got more confident some of them actually started saying yes and after a couple years dating just felt easy. I'm not really a good looking guy so yea, even in my prime the rejections outweighed the successes pretty heavily but they didn't hurt and most girls are used to being hit on so it's not nearly as awkward as you might think it is when they say no.