I get the impression from some that it is almost impossible to perform a mortal sin, as the requirements for committing one are so strenuous that it is difficult. But from others I get the impression one can barely breathe without committing a mortal sin, particularly if you list pride or envy or lust or something as something you constantly struggle with.
To me sin is deceitful. Part of its power is its ability to hide, and its power for me to make sure it stays hidden, usually by my own will. So a strenuous search for mortal sin may turn up empty, or with only a token sin that’s mortal that will cover all the others.
How can you be sure you did a good confession?
God is the best and most perfectly loving of fathers. He wants us to be with him, he wants to free us from the bondage of sin by means of our self-awareness, self-improvement and his great gift of the sacrament of confession. None of these aims are achieved if he harshly and unfairly damns us for sins that we are genuinely unaware of.
If we make a sincere effort to examine our consciences, and ask for His guidance to uncover everything in which we have sinned, so that we may confess properly, he won’t let us be steered far wrong.
Read the Gospels about the prodigal son. I think it speaks volumes that the father actually goes out to meet his son on the road as he is returning - so God is willing, to a considerable degree, to meet us exactly where we’re at. Not so we stay there, but to help us reach higher and become better.
There are some pretty good examination of conscience guides that are very helpful as well. Personally I really like the one written by
Fr Robert Altier
By the way, most Catholics don’t believe that people are inherently terribly wicked or self-deceiving or anything - simply that we have tendencies in that direction. Christ said to the woman who anointed his feet ‘many sins are forgiven her because she has loved much’.
And I think that’s the key and the saving trait of humankind, that we are capable of great love for God as well as each other. As long as this is our strongest guiding characteristic (and I pray every day that he makes it so for me!) again, we won’t go too far wrong when it comes to sin or to confession.