Rumplestiltskin

Charming fairy tale where a mother is unfairly expected to give up her firstborn child?

OR

The story of a woman who unjustly breaches a binding agreement because she later discovers that she'd just rather not abide by the terms of the contract?

The hero of this story is Rumplestiltskin.  He saved her bacon by spinning the straw into gold, then offered her a way out of the contract (remember, he'd fulfilled his part of the agreement) and when she successfully guessed his name; he abided by the terms of the new agreement!