Hi Sage and an "official" welcome to piecing although I have seen you have visited other threads here for a while, so you're no stranger, but glad to see that your story fits in here.

Quoting sage:
What should I be doing instead? I think the biggest 180 would be to not withdraw -- to maintain a positive attitude, to not dwell in thought patterns. To be supportive of H's normal changing moods by accepting him just as he is.
Acting "as-if" can play a big part here as well. Act "as-if" he might be a little nervous in the beginning of the occasion. That he might be worried about making sure you have a good time. This should help keep you maintain an upbeat and light-hearted PMA and ease his mood and make him feel more comfortable. Maybe even come up with a "ice-breaker" ahead of time to fall back on to help if things seem tense.

See ya around ... so 'til later...
KAW