Basic rule for sysadmins:
Never deploy on Fridays.
If you do, it's a guarantee things will get screwed up. If you decide to to it first thing Monday morning, the same thing will go well. It's technology.
Still, we deployed the third installation of a subsystem this Friday and everything seems to have worked fine. Why?
1. We had done it before.
2. We formalised the procedure into an up-to-date checklist.