The old rebbe explains in the 28th chapter that even if the bad thoughts fall to his mind while he is praying or learning Torah, he should push them away. And he should not try to develop the source of the bad thought and turn it into good, since that is the tsaddiks job, that when a tsaddik knows that someone else has a bad thought, he takes the source of that bad thought and turns it to good. But if the bad thoughts fall into his mind, he cannot do that since it is a part of him. However, he should not be sad about it, rather he should continue to pray and to learn Torah out of happiness, through thinking that just like when two people are fighting, if one strengthens himself, the other one will strengthen himself even more. So is it here, the bad thought came into his mind just because was praying and learning very good. And if he thinks this, he will strengthen himself even more to serve G-d. and not as the world says, that this that the bad thought came to his mind is a proof that he did not pray so good, because they would have been right if the person only had one soul, which prays and thinks the bad thought, and therefore if the bad thought comes to his mind, it is a proof that he did not pray good. But really one has two souls, one prays, and the other one tries to fight it. And this is like one who is praying, and someone else is standing in front of him and tries to disturb him, which in this case he should not answer anything back, because then he will go down to his level, so too here, he should not try to interact with the bad thought, because the one who interacts with a dirty one gets dirty too. And if it is hard for him to ignore and push away the bad thought, he should ask G-d and pray to him that he should help him with it.