A friend was worried and jittery about an event he'd been preparing for a while now. He just wanted it to be over and things to not go wrong. I told him not to worry, that he's already done the best preparation he could and that no matter what things will surely work out.
It's easy to fall into the trap of anxiety, overthinking things that might go wrong, or things that might not go according to plan, and so on. And you know what? It's fine. Not everything goes according to plan. Unexpected things happen. People understand. We laugh about it and move on.
I fall into this trap often. I try to tell myself that worry does nothing. If there's something you can do to make things better, then do it. Otherwise, why worry?
If you can't get past your overhtinking, I find that it sometimes helps to think about the worst-case scenario. You're already worrying about problematic things happening, so why not go all the way right? Often you'll find the worst-case scenario is something survivable, and it's so ridiculously out-of-left-field that the rest of the worries just fade away.
Life is too short for worrying.