i have read that it is a good pratise to confess previously forgetten sin that where overlooked.ie when i came back in my first confession if i where to list the number and types of sins i might just be getting out of the confessional now.sincere contrition is the main component of a good confession.there is one sin of mine that although i haven’t confessed it i know i was forgiven of it,like the op stated i just didn’t know it was really that serious like i do now.i once lived a life full of mortal sin yet still recieved comunion( only on an ocassionaly basis) in a state of mortal sin,i would recgonize my life going even further in the gutter and i would try to go to mass to recieve the Eucharist in an atempt to halt the downward slide.since i didn’t beleive in the church there where many doctrines of the truth i didn’t believe in,about the only thing i beleived in was the Eucharist and even at that i beleived one recieved Christ in communion in any church that taught a beleif of the presence.but now due to the Grace of God i am where i belong and sumbit to the Christ given authority of His church,and no other "church"will ever cause me not to be member of His one true holy and apostolic church.