I am quite vigilant
Something of an understatement there, Sam!

I think to respond to the reheat question - by reheating to "piping hot" you kill a significant proportion of bacteria (say 99.994% - figure pulled out of my backside) If left for more than 12-24 hours, the bacteria have time to grow to much larger numbers, so that killing this proportion is no longer "safe"

Oh, yeah, and the fruit salad thing. I've never forgotten that from my food handling course - how many people wash melons? You figure "Oh, well, you don't eat the rind..." BUT you do use the same knife to cut through it as you do to cut the fruit. And when you buy a cut melon from a grocer, do you have any idea whether they have washed it? At the course, we were told that melon is a really high risk food for the immune-suppressed.
also that hospitals wash lettuce in a weak bleach solution. Mmmmmmm....