"It will happen when you least expect it."

Hi, I am a 21 year old virgin, and whenever I was feeling down about never being in a relationship or never having sex many people, including my friends, have all said, "It will happen when you least expect it." I believe them of course, but I want to know the logic behind it. My two best friends who have girlfriends both said they didn't expect it to happen. My assumption is that if I continue to work on myself, and only think for myself, then when the opportunity arises it'll be completely unexpected because I was focusing purely on myself. What do you think?