New MacBook Air User: Durability?

I just purchased a MacBook Air (13 inch, 256 GB) this week. Overall I'm happy with the laptop, it's extremely light and fast, but I have a question about durability.

I find that if I'm writing a paper for school, and I'm typing really fast on it, it's a little flimsy. It moves on the table with just a little push. I've noticed this more on some tables than others, but it's annoying me. Has anyone else experienced this? If so do you have any advice on what to do? It seems like the left side is more stable than the right, maybe there's a problem with the rubber foot on the right? I don't know why I'm letting it bother me so much. I guess because I'm a college student and it was a pretty expensive purchase for me. Any assurance would be really helpful. Thanks.