Variables won't, constants aren't.
If it's green or wiggles, it's biology. If it stinks, it's chemistry. If it doesn't work, it's physics.
An infallible method of conciliating a tiger is to allow oneself to be devoured.
Money isn't everything. It isn't plentiful, for instance.
A word to the wise is superfluous.
A milligram of prevention is worth a kilogram of cure.
A bird in the hand is inconvenient.
If at first you don't succeed, you've got one strike against you.
Early to bed and early to rise and you'll be groggy when everyone else is alert.
People who live in stone houses shouldn't throw glasses.