You shouldn't feel bad about missing him, it's only natural to feel this way after a breakup!

Something I've found is that the more I try to stop myself from thinking about something, the more I actually think about it; so it might be better to just let these feelings run their course. In doing so, you'll become less and less attached to them. You could even try a simple form of meditation to make it easier to become detached - which will happen, eventually.