Sometimes the best way to get the nasty things you joked about in the past out of your mind is to start doing more positive things with your life.
Before you know it the positivity in your life will grow to such proportions will not allow room for the nasty thoughts.
It seems to me that if you are troubled by it this much, that you are asking on a forum for questions, you might want to talk to your religious adviser
Just a thought. :o)