Would one off night ruin it?

I developed a major crush on my friend and the two of us hung out one night and sparks flew the entire time. We spent three hours talking and chilling and he invited me back to his place though I couldn't go. However, when we hung out a few nights later it was not as good. Things seemed kind of forced and there was no spark. However, I'm wondering if we were having an off night since he was sick and I was super exhausted. Since then things have been too platonic and I don't know what to do. Should I just let it go?