I’ve been reading Mere Christianity lately, and I ran across this paragraph and think it says so much.

Good and evil both increase at compound interest. That is why the little decisions you and I make every day are of such infinite importance. The smallest good act today is the capture of a strategic point from which, a few months later, you may be able to go on to victories you never dreamed of. An apparently trivial indulgence in lust or anger today is the loss of a ridge or railway line or bridgehead from which the enemy may launch an attack otherwise impossible (Lewis, p. 132).

This is why we need to resist any and all sin constantly. If we don’t, one leads to another to another to another. Before long, we’ve lost our way and are mired in things of this world. But it’s also why when we take small steps in the direction God wants us to go, the steps get greater and greater.

— Lewis, C. S. (1952). Mere Christianity. New York, NY: Harper Collins.