rats in the cellar & rotten fruit

when I come to my evening prayers and try to reckon up the sins of the day, nine times out of ten the most obvious one is some sin against charity; i have sulked or snapped or sneered or snubbed or stormed. and the excuse that immediately springs to my mind is that the provocation was so sudden and unexpected; i was caught off my guard. [...] surely what a man does when he is taken off his guard is the best evidence for what sort of a man he is? surely what pops out before the man has time to put on a disguise is the truth? if there are rats in a cellar you are most likely to see them if you go in very suddenly. but the suddenness does not create the rats: it only prevents them from hiding. in the same way the suddenness of the provocation does not make me an ill-tempered man; it only shows me what an ill-tempered man i am. the rats are always there in the cellar, but if you go in shouting and noisily they will have taken cover before you switch on the light. apparently the rats of resentment and vindictiveness are always there in the cellar of my soul.
-c.s. lewis, mere christianity

no good tree bears bad fruit, nor does a bad tree bear good fruit
-luke 6:43