Interesting match. What a comeback by your opponent. I guess there are a couple of things to say.
First, Banshee harass wrecked your economy, so while you were beating down your opp's door, he was evening out the disadvantage by slowing your economy/production/etc. So, note for next time to pull observers back.
Next, you had Zealots simply sitting in his main for a long time doing nothing. In the chaos, remember to send one to each resource spot to stop him from rebuilding (could have sent 1 to each main base location and set it to patrol the natural expo at each.
Basically, it seemed like you went all-in to end the game when you had a huge advantage already. That's cool. I may have done the same. But I guess from watching the replay, there are ways you could have prevented his comeback by pulling obs back to stop the harass and distributing your units to areas of the map where he could rebuild.