Unless the thing you're confessing about could put you in jail. But if it's something along the lines of, "I know you really like your Ho-Ho's dude," go ahead and own up. You'll feel better about it.
But you shouldn't think that confessing is an across-the-board good idea. For example, let's say that about six months ago you killed a rapist. You were just walking through the park looking for someone to sell you some acid when you heard a woman's muffled shouting. You stepped over a fence and pushed through some bushes to find a man pinning a woman down in the grass, the dull edge of his knife pressed into the corners of her mouth.
You shouted, "Hey!"
The guy wheeled around at you. His eyes were yellow with bright red bulbs in the center.
The woman kneed him in the abdomen and wriggled free. He grabbed at her pants leg but she took off. You never saw her again.
The guy got up and came at you. The sharp edge of his knife was coming right at your nose. He was smaller than you but a lot stronger. He had you on the ground. You were holding his knife hand away from you, but the knife was coming closer. You were growing weaker. You were about to die.
Your left hand scrabbled in the grass and found a rock. You swung your left arm up from the grass and cracked the rock into the back of the rapist's head. When the rock hit his skull, the yelp that came out of his mouth sounded like he was gargling mouthwash.
You rolled him off of you, stood, then saw the blood in the grass. It was coming near your shoes. You ran.
The next day, you read about the dead man in the paper. The story told nothing of an attempted rape. It only told of a dead man who'd been arrested for burglary in the past.
You read the paper every day for a month, but the story disappeared after less than a week. Never was there any mention of an attempted rape.
If that's the kind of thing you were thinking of confessing, that kind of "murder in self-defense resulting from a prevented rape that you can't prove," keep your mouth shut.
But if you ate your roommate's Ho-Ho's, by all means wipe the slate clean. Unless you can't afford to replace them. Then blame his buddy Ken.
Happy Confess Day!