As someone who also grew up Catholic, i definitely understand the whole confession/guilt thing. I always laughed about "Catholic guilt", but without realizing it (until it seems to be too late), it appears to have taken hold and i can't quite shake it. That being said...
I rarely lie. I learned when i was very young that, with few exceptions, honesty is by far the best way to go about things. Now, for whatever reason, i find it very difficult to lie. I've found that being honest about screw-ups earns others' respect and trust because they know that you won't b.s. them about things, even if the blame lays with you.
As for the actual act of "confessing", i find it very freeing to unload everything - what i've done, what i haven't done, what i should've done, how i *really* feel about that bitch at work.Even if i know i'll get in trouble if i admit to failing to do/not do something, i feel like i need the punishment to move on with my life; i need someone else to absolve me of my "crimes" before i can let go of things. I think that even without being raised Catholic, i would be like this with respect to failure and confession. I feel very responsible for the happenings around me and carry that weight with me; i take it very seriously and personally when things don't happen as i think they should and i'm responsible for them. I feel like i'm letting the world at down. Being able to lay my shortcomings out and have someone else judge them and allocate punishment as necessary takes off a lot of the weight and definitely makes me feel better about my far-from-perfect self.