How to cut it off with someone you’re dating

Hi there so I was seeing a guy (we aren’t exclusive or anything) but we’ve gotten quite close I guess. I’m going to call it quits though and I was wondering how to do so?

I don’t want to hurt him. I’m ending it for self improvement reasons and the fact that I don’t think I see him as a boyfriend just a best friend

Can anyone help me with what to say??