When we pick fruits from a fruit basket, if we find a rotten one, we put it back and take a good fruit. Likewise, when we have a bad thought, we may think that replacing that with a good thought is a simple solution. But like that rotten fruit remaining in the basket, the bad thought still remains only to pop up some other time. True permanent solution is to remove all rotten fruits in the basket. Likewise only the chanting of Mahamantra can fruitfully flush out all the bad thoughts from our mind.| HH Sri Sri Muralidhara Swamiji