One of my favorite quotes of his, from Fix the machine, not the person:

[When a] system isn’t working, it doesn’t make sense to just yell at the people in it — any more than you’d try to fix a machine by yelling at the gears. True, sometimes you have the wrong gears and need to replace them, but more often you’re just using them in the wrong way. When there’s a problem, you shouldn’t get angry with the gears — you should fix the machine.

...You can’t force other people to change. You can, however, change just about everything else. And usually, that’s enough.