From Volume III of the “Collected Letters of C.S. Lewis” edited by Walter Hooper:
Dear Mr Karlsen-
Your letter did not reach me till to-day. Of course I have had and still have plenty of temptations. Frequent and regular prayer, and frequent and regular Communions, are a great help, whether they feel at the time as if they were doing you good or whether they don’t. I also found great help in monthly confession to a wise old clergyman.
Perhaps, however, the most important thing it to keep on: not to be discouraged however often one yields to the temptation, but always to pick yourself up again and ask forgiveness. In reviewing your sins don’t either exaggerate them or minimize them. Call them by their ordinary names and try to see them as you wd. see the same faults in somebody else – no special blackening or whitewashing. Remember the condition on which we are promised forgiveness: we shall always be forgiven provided that we forgive all who sin against us. If we do that we have nothing to fear: if we don’t, all else will be in vain. Of course there are other helps which are mere commonsense. We must learn by experience to avoid either trains of thought or social situations which for us (not necessarily for everyone) lead to temptations. Like motoring – don’t wait till the last moment before you put on the brakes but put them on, gently and quietly, while the danger is still a good way off. I wd. write at more length, but I am ill. God bless you.