When I still had my IT business at some point I took on doctor's offices as clients. It was a great step up for me but they all wanted contracts with a 24h support build in.

I never felt so miserable even though the money was good. The constant worry of a potential phone call would be enough for me to not go and do things.

What helped was getting a good backup partner. Someone reliable. The feeling of responsibility was always there but it made the worry go away.

Good luck with the release today!