There was a time that I felt the same way that you do. What I later discovered is that the reason for hanging on is due to lack of finding out which way it might go had we gone out.
In my case, that chance came up. The guy’s girlfriend called me up to say that he was moving to my area and asked if I needed a roommate. I invited him over for dinner, and he ended up moving into the same building. It didn’t take long to learn that we were not meant to be a couple solely based upon personality differences. Plus, I got to know his girlfriend better and saw that they were an ideal match. They are still happily married almost 30 years later.
There are also situations where two people meet up again later in life and get together. And it works. You have to either go for it or learn to live with the possibility of “What if?”. The former is the better way to go.