why the guilt?
Because for much of your young life everything naughty you do has to be confessed to a man who then gives you prayers to say to make up for it
And because most people start this at about age 7, sometimes younger half the time you can't think of anything so you make it up, and then feel guilty about that.
Thangs I was taught at school, OK so nobody is worshiping a golden calf, but if you care about your football team / favorite TV show / chocolate cake this is worshiping a false god.
Sex, if you are not married and if the sex doesn't leave you, 'open for conception' you must feel guilty.
If you are in pain, "offer it up to god, don't take a pain killer"
Looking in the mirror too long, check you race isn't dirty and your hair is combed and that's enough.
Eating meat, but only on certain days, not fasting, but only on certain days. Our school cooks were not RC, so when they forgot it was a day of abstinence and cooked meat the head had to telephone the bishop to get dispensation for us to eat it.
Oh and the time someone brought in a copy of a book published by the Jehovah's Witnesses - wow I think people were in confession for weeks for just looking at it.
A tiny number of RCs use self flagellation, that adds a whole new layer of guilt, have you beaten your self enough? Have you done it too much?