If a man was sorry for stealing only because he was caught and had to go to prison for it, his sorrow would only be natural. Or if a boy was sorry for telling lies only because he got a whipping for it, his sorrow would only be natural. Or if a man was sorry for being intoxicated because he lost his situation and injured his health, he would not have the necessary kind of sorrow. If we are sorry for having offended God on account of His own goodness, our contrition is said to be perfect. If we are sorry for the sins because by them we are in great danger of being punished by God, or because we have lost Heaven by them, and without any regard for God's own goodness, then our contrition is said to be imperfect.
Imperfect contrition is called attrition.
When I say that our sorrow should be universal, I mean that we should be sorry for our mortal sins without exception. If a person committed ten mortal sins, and was sorry for nine, but not for the tenth, then none of the sins would be forgiven. If you committed a thousand mortal sins, and were sorry for all but one, none would be forgiven. Because you can never have God's grace and mortal sin in the soul at the same time. Now this mortal sin will be on your soul till you are sorry for it, and while it is on your soul God's grace will not come to you.