I'm not worth this much energy

[Counselor]

I did something stupid. I had a rebound relationship with someone ten years my junior, and it lasted four months to the day. I knew about two weeks into the relationship that it was not going to work, we barely knew each other before we started. When I tried to call it off, he started protesting and crying and demanding reasons why I felt we should stop. He's a sweet kid, but he's just that; a kid. I got him to agree to break it off, but now he texts me how much he misses me twice as much as he did before. I want to be nice to him, and I want to tell him to grow a pair and stand up for himself, and I want him to be okay. I know it's not my responsibility, but I feel like I'm responsible for his attachment to me.

How do I comfort him without reinforcing his attachment?!