I find that one often doesn't realize the gravity of one's own sins.
However, when forced to disclose them before another (priest) they take on new meaning.
The priest acts as a doctor for our soul. He hears our most inner thoughts, and fears and insecurities. He alone (of humans) is aware of what we are going through, and he can therefore, prescribe a cure.
For example, I go to Confession and I say that I stole something. I say I am sorry, I repent, etc. I get absolution.
I come back next week, and I say the same thing, again. The priest might give me a bit of lecture, etc.
I come back the following week, and again I have stolen. The priest now realizes it was not a one time thing, but, I have a problem. He will suggest various methods for me to be "cured" of this bad behavior - prayers, good deeds, reading Scripture, etc.
Finally, if I continue with the same sin, he may actually deny me Holy Communion until I have mended my ways. Denial of the Holy Sacraments isn't meant as a punishment, but, a time to heal, and make yourself worthy to receive the prescious Gifts.
Does that make sense?
Even while physcially on Earth, Christ had his disciples healing people, and banishing demons, ...
Mark 9:28 When He came into the house, His disciples began questioning Him privately, "Why could we not drive it out?"
Mark 9:29 And he said unto them, This kind can come forth by nothing, but by prayer and fasting.
From the above statement, it is clear that the disciples had been driving out evil spirits from people, and had in this intance encountered a rather stubborn demon, whom Christ expelled. Therefore, we see that Christ did entrust His flock to His disciples. We are still His flock, and our clergy are His Disciples.