Wouldn't. Wouldn't carry a vast different meaning from couldn't.
Choose it. Choose it well.
Don't hide behind reasons. A coward will always do it.
Sometimes we need reasons to justify our actions. However, sometimes, inexplicably, we do not have a reason to carry out any action. That's why in murder case, murder without intention is pardonable.
*erk, salah example*
Anyway, you wouldn't do it. But actually, you couldn't do it.