The Lord's Prayer covers all sins and if that isn't enough David said forgive the things I have forgotten and cannot remember. Bring them to my attention.The thing is.....we sinners have NO IDEA in comprehending (let alone "counting" like doing sums on an abacus) each and every one of our sins day in and day out. There is NO realistic capacity to repent of every one of them.
Martin Luther tried though. He really did.
I think we can confess our sins by the example we have from the Word of God.