"God pardons what is past, then, but for the future we are each responsible for ourselves. By repenting we condemn our past misdeeds and beg forgiveness of the Father, the only one who can in his mercy undo what has been done, and wipe away our past sins with the dew of his Spirit. And so, if you are a thief and desire to be forgiven, steal no more. If you are a robber, return your gains with interest. If you have been a false witness, practice speaking the truth. If you are a perjurer, stop taking oaths. You must also curb all the other evil passions: anger, lust, grief, and fear. No doubt you will be unable all at once to root out passions habitually given way to, but this can be achieved by God's power, human prayers, the help of your brothers and sisters, sincere repentance, and constant practice."
The last efforts in the list are efficacious because they are suffused by the first in the list: God's power. That's the great secret of salvation. We can save each other because God is at work in us saving us.
Clement of Alexandria (AD 150-215), Quis dives salvetur, 39-40: PG 9, 644-645
Clement was the director of the catechetical school of Alexandria for a time and may be considered the founder of speculative theology. Not a bad rep, if yask me.