Boss treating you unfairly? Deli counter guy put mayo on your pastrami again? Relatively certain your wife/husband is cheating on you? Well today's the day to hold it all in!
You know what you should say and you know what you want to say and you know there's nothing worth saying until it all gets said. But hey, why make waves? Besides, that knot of frustration in your belly has been with you so long it's practically your best and possibly only friend. Why not give it a name, like Ben, and tell Ben your troubles until Ben turns into a malignant tumor? Or you could continue to have imaginary arguments while alone in your car. You always win those!
No one likes a complainer. So, whether your boy/girlfriend didn't come to your birthday party or your roommate used up all your insulin, just let it fester. Because today's Hold It All In Day!