We all cope in strange and different ways. There have been times where I have laughed and smiled during really inappropriate times. I remember when I first found out a friend of mine died, I started laughing. It wasn't that I'm a heartless person and didn't care, but rather, I was unable to accept the reality of the situation and afraid to express my feelings around anyone. I hate that feeling of appearing weak in front of other people. It makes me feel so vulnerable and helpless.

To answer your question, I believe it is very common to express yourself in strange ways. Everyone is different and some people have trouble either laughing or crying. I would feel grateful that you can do both!