The best CFI can't fix poor decision-making...
true, but he can drum things into his students constantly. mine did. i'm sure the cfi's on here will say the same thing.....keep drumming it in, and it'll take hold.
bob has a tendency to bring "problems" onto the airplane with him. and i always seem to find them. but....thanks to his style, i've landed with partial engine failure, and with total electrical system failures.....the electrical system pooped out at night......and both times were non-events, that could very easily have turned very very bad, without the guidance of a good cfi. he wasn't onboard for those btw.......but i'd dealt with both instances simulated many many times.
he also had a good habit of making sure his students understood the "whys" of what he was instructing.

understanding the "whys" leads to it sticking in ones mind to make better decisions.