Don't infect others with your bad mood.

When you go out in public with a cold you would never dream of coughing and spreading your germs all over.  Your face can cause more damage then your germs.  When you go around in a bad mood with a miserable face, you are spreading that bad mood and infecting others.

from a Shiur on Torah Anytime:

Rebbetzin Esther Jungreis: Teshuvah - Guaranteed Happiness

Is it worth it?

There is a sickness in human nature that we always want what is forbidden to us. When something is really tempting you strip away the element of temptation from its being forbidden, the "glitzy garment" and ask yourself if it is really worth it.

from a Shiur on Torah Anytime:
Rebbetzin Esther Jungreis: Teshuvah - Guaranteed Happiness