Immediately go read the Theory of Poker by Sklansky. Re-read it. Then read the parts you did not understand once again. This is a fundamental concept that you need to understand to have any hope of consistently making correct decisions. In limit, pot odds dictate when it is correct to chase and when a check-raise can give incorrect odds for others to chase, among other things.
I won't pretend to be able to explain pot odds, implied odds, and reverse implied odds and how they apply to no-limit to allow you to put maximum pressure on your opponent with a correctly sized bet, or whether to chase yourself. I just try to come close when I play in the odd tournament or two.
Go read Sklansky. If you want to be succesful at our game, you need to get over your aversion to numbers.