I had this conversation two days ago. I tried to force myself into making a childhood crush (who I grew up with kindergarten to 13) work, and I simply just did not like the adult version of him. I did it again when I saw a guy I dated in my early 20s on OK Cupid. I quickly remembered he was a pathological liar because he was still a liar on his late 30s. I even had a really good friend who I dated shortly, and I got in touch with him on Twitter. Royal asshole. Blocked him. Folks really do need to leave the past in the past. Now if I see an ex (and it took me 3x to learn) my response “Hello. How are you? Don’t tell me. Gotta go. Bye!” There will never be a number four.