Foolproof systems to not take into account the ingenuity of fools.
The bridges that you cross before you come to them are over rivers that aren't there.
The really tough thing about humility is you can't brag about it.
The toughest thing about raising kids is convincing them that you have seniority.
One good thing about being young is that you're not experienced enough to know what can't be done.
The trouble with making intelligent suggestions is that you're apt to be appointed to carry them out.