If a hungry lion suddenly appeared, you'd be terrified. So...

If a hungry lion suddenly appeared, you'd be terrified. So terrified you'd probably run away. Great, fear's doing its job. But you might get so afraid that you lock up and can't move. This would be very bad. Guilt's the same. It can prevent you from fixing the situation, make you feel so bad you can't function at 100% and even lead to more guilt-provoking bad behavior.