I feel pretty lame asking for help with something so simple but I have a tendency to get anxious and over think this kind of thing.

This semester I was part of a group project and one of the guys and I got along quite well. I would like to send him an email saying I want to keep in touch but I don't know what to say and I keep psyching myself out. I'm really bad at reading people so I keep worrying that he was just being nice and he isn't interested in becoming friends. I intended to tell him to keep in touch after the last class but when we got to our cars he just said "Well, bye for now" and I chickened out :/

What should I say? I want it to come off as casual and like it's no biggie if he's not interested in being friends but everything I write comes off as awkward.

I'm not good at this sort of thing.