Just be yourself. You are not the one that has to worry about how to act, i.e., your h is the one that needs to worry.
Treat him as you would a salesman, i.e., smile and make small talk if he comes over to you...otherwise, socialize w/the rest of the group and try to enjoy yourself.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
