I'm going to the cottage with the boys instead of seeing a baseball game with my girlfriend
Why are you choosing to hang out with your friends instead of your girlfriend?
The boys want to go drink and have a blast together
It's okay to want to spend time with your friends as well as with your girlfriend, but you should honor the plans you have made.  Your girlfriend was planning on seeing a game with you, so you should respect that.
I'm a free person and my boys need me more. I'm the life of the party. I want to party, drink and fuck and do it all with the boys.
You should make your girlfriend a priority when you already have plans with her. It's wrong to neglect your relationship. Doing this will make your girlfriend feel as though she is not important to you.