If I don't have a measurable goal for non-sports based fitness, I will stop doing it.
The strength aspect is easy enough to measure. That said, I've taken it to heart that one should never, ever miss a lift (unless you're going for a world record). A number of my personal bests were done easily and I could have added 10-15% to the lift, but I always left it for another day. As you noted, when you are at the very edge of your strength, bad things can happen.
(And for the record, those easy PR's I mentioned above, I'm sure I looked like I was passing my first shit in five days but everything was under control).