No one needs to know you are having an affair or that your spouse just left you. Do not brush off anyone who wants to talk to you. It doesn't matter whether or not you liked that person in high school. We have all changed. Bring an extra hankie, and cry all you want when you are overwhelmed by nostalgia and old friends.
Tears can be a great catharsis.
All responses to questions should be at least two full sentences. Don't be abrupt. It will make you appear snobbish. Don't do too much bragging. It puts a spotlight on your insecurities.