In reply to keith-ratcliffe:
I always applied this to flying. My '3 strikes' rule.
There's always rules and regulations that will ground you but one day I took off, the weather was borderline, I had one dodgy passenger (alcohol) and then one of my fuel pumps went u/s. None of them were enough to put down on the ground but dealing with all 3 at the same time could've proved problematic if a real emergency cropped up.
So when the working day had finished, I reassessed things and always applied my 3 strikes and we're on the ground, rule.