Avoiding the cake doesn't mean you have to avoid having a social life. Try to remember that (I have to remind myself too).
Last weekend, my fiancé and I went to our friends' birthday party. They ordered pizza for everyone (20-25 people) and ordered a salad for me instead. Most of the guys drank beer while I had two glasses of wine. I had a blast and no one gave me a hard time the entire night.
I would have loved to be able to eat the cake and pizza with everyone else, but it just wasn't worth taking insulin. Plus, it's not as if your discipline isn't rewarded in other areas of your life. It's pretty hard to get fat eating salads.