A - Thanks for the great questions! I love the Sacrament of Reconciliation, so I am glad that you have a great interest in it.
Let me first quote a bit from the Catechism of the Catholic Church on Reconciliation:
1422 "Those who approach the sacrament of Penance obtain pardon from God's mercy for the offense committed against him, and are, at the same time, reconciled with the Church which they have wounded by their sins and which by charity, by example, and by prayer labors for their conversion."
Notice that we seek both forgiveness and reconciliation with God. This leads to conversion and in the entire process we are given the grace of God.
Our purpose in this Sacrament is to be brought closer to God, esp. when we have severed ourselves from His love by committing mortal sin.
So, would we be punished in hell for a mortal sin that was not confessed even though our intent was to confess it and be forgiven? No. God is merciful and cares about the heart, which was already seeking out His forgiveness.
Now, we do still have to pay the temporal price for our sins either in this life or by purgatory. So, there would be a cleansing in purgatory before we entered into heaven, but our salvation is assured if we die in a state of grace.
The question of how often to go to confession I will answer in both legal and practical ways:
The Church requires we go once a year during the Easter season, if we are in the state of mortal sin. But, as a general rule of thumb it is a good idea to go about once a month. I recommend that most people schedule it so they don't put it off too long.
I know that I have several tendencies that confession helps me with. I am too scrupulous and I am too prideful. Confession helps keep my head balanced better between the two.
If you commit a mortal sin, the best thing to do is to do the following:
- Don't beat yourself up too much, because the devil wants you to think you are no good.
- Don't trivialize the sin, because we all have a tendency to try and rationalize.
- Go to confession as soon as is feasible and remember that if you are not in a state of grace then you shouldn't receive Communion (this in and of itself would get me running to Confession).
- Ask the priest for tips on how to avoid the near occasion of sin so that you can continue to grow closer to Christ and resist temptations.
I hope this helps.