He's leaving and I'm hurt

I knew what I was getting myself into but did it anyways. I was seeing this boy over the summer and he's going back to school in about 2 weeks. Now I'm all in my feelings and sad and hurt. But I feel like I was dumb for doing it because I'm a long relationship person but I knew that wasn't going to happen with him, but I did it anyways. Which was so stupid. I should have forgotten about him. Now I don't know what to do because I'm all sad and I really like him. Should I distant myself? To make it easier.