Spend some time figuring out what feelings were triggered, and why. Are you afraid of something? Angry? Insecure? Feeling deprived?
Have you read Tacit's broken fridge article?
It's difficult to control emotions, it is more realistic to control behavior. So, think about possible courses of action you could take and what the logical results of that behavior would be- and if that's what you want.
So, if you're afraid of losing him, and one behavior would be to tell him not to do X activity with anyone but you, but then he'd resent not being able to do X with various people he's used to doing that activity with, and eventually he might get sick of dealing with your insecurities and leave you, then that's not a very productive course of action.