That overthinking thing is me allover, my fellow INTPer. Analyze it from all angles until you talk yourself out of it. To me, that is one of my worst traits. You have the right idea. Live for today. Tomorrow will come without our approval. Tomorrow will work itself out.
I am really trying to say YES more, instead of thinking of the possible scenarios why it would be a bad idea.
It is a hard habit to get out of, I know. Oh btw, I did a post last night here. I took the advice of @fieryfootprints and put a poem in a separate post. It was about a post @escapist did a few weeks ago. If you have a chance, give it a look. Also, I don't think she has seen it.