How do i get over this?

My boyfriend and I have been dating for two years now. He had never really had the opportunity to do many things that I have like snowboarding, fishing, etc and i have introduced him to a lot of new things. Now everytime he goes and does something we both have never done i thinki we should be doing it together. For example, we both have never been to the ski resort close to our city and he went and then i got mad at him for going. Im over it now but things like this always come up and i just dont know how to not be mad. Can anyone please help.
* Now when i say mad I dont actually get mad...more of to myself and then quickly getting over it but I dont want to feel this way anymore.