I heard a really good analogy for explaning mortal vs. venial sins.
Picture this. We are connected to God by an intravenous tube. We are fed through that tube. If we commit a mortal sin (example, murder someone) then we cut ourselves completely off from God - the intravenous tube has been completely clamped, no flow through the tube. If we commit a venial sin (example, lie to someone) the flow through the tube gets inhibited a bit, but the flow is not stopped. God does not cut us off, we cut ourselves off from God.
Just to add to what soutcitymom said about confession, one does not receive forgiveness from the priest, but the priest acting for God, so to speak. In additon to forgiveness, we receive God's grace. After we have been forgiven for the sin, God's grace helps us to avoid the pitfall of that particular sin. As an example, let's say I have a big fight with my husband, and we live in icy silence for a week. I am dwelling on my anger, and am miserable, and need help to get past it. I can go to a priest, confess my part in the fight, and declare my desire to avoid such fights. Depending on the priest, I may be given a prayer to recite (3 Hail Marys), a biblical passage to read, or be told to do some other act (do 3 loving and considerate things for my husband) The grace that comes from the confession helps me to avoid the fight next time. As I am about to lose my temper, my self-control might kick in, and I might be able to say, ah, it's not worth it to get into a fight about this. God's grace gives me the ability to do this.
I have come to rely on confession a great deal. For me, it helps me to be a better person. It heps me to have the humility to say "I'm wrong". It helps me to see my part in a conflict, and helps me see what I need to work on (my anger, my pride) Confession has seen me through some rough times. It is something that has to be experienced to fully understand. It is not humiliating, it is liberating. When I come out, I feel like a shiny new dime, with a fresh start and resolve to do better.
It helps to have a good priest you trust and feel comfortable talking with openly. I am fortunate to have 3 priests I see regularly for confession and spiritual direction.
I hope I have helped to cast a positive light on confession.