Rule 1. All magic comes with a price. We hear this frequently, from Rumpelstiltskin. He seems to have an acute awareness of the cost of magic, and he's also very prone to twisting words to suit his purposes. This seems to be the one statement that is true to his character - whether Rumpel or Gold. He's a powerful and calculating individual. This is just a way of saying that all actions have consequences - often beyond what we can perceive.
Rule 2. Any curse can be broken. We've seen two curses activated - The Dark Curse and the Sleeping Curse. The other magic we've seen work as a curse is Midas' Golden Touch. Which isn't, strictly speaking, a curse. If we take almost any version of Midas's story as true, he *wished* for the golden touch - it just backfired.
Rule 3. True Love is the strongest magic/Any curse can be broken by True Love's Kiss. This is the one we've seen fail most egregiously. Rememeber Fredrich? Also, True Love does not need to be Romantic Love - it just makes for better TV.
