Just sort of relax your mind and say yes, it does hurt, I know. Don't try and shut it out.
And I came to believe that good and evil are names for what people do, not for what they are. All we can say is that this is a good deed, because it helps someone or that's an evil one because it hurts them. People are too complicated to have simple labels.
Gradually, at various points in our childhoods, we discover different forms of conviction. There's the rock-hard certainty of personal experience ("I put my finger in the fire and it hurt,"), which is probably the earliest kind we learn. Then there's the logically convincing, which we probably come to first through maths, in the context of Pythagoras's theorem or something similar, and which, if we first encounter it at exactly the right moment, bursts on our minds like sunrise with the whole universe playing a great chord of C Major.