I have done that too. I just drink until I can relax more around people and "open up" more, but not too much. I agree with s4 and Maranara, that you were at a reception, and that I would think that people had more to drink than you.

I don't really know how to avoid feeling the shame/negative feelings that creep in, but maybe try to focus on the fact that you did end up having a good time?