He will be able to develop his character to perfection and take on the yoke of heaven with a perfect heart. He will be worthy of true prayer and perfect repentance, and bring about unification in the worlds above and the worlds below. The hidden Torah of the Ancient One will be revealed, the forces of evil will be destroyed and the forces of holiness will be elevated. All the thoughts which pass through the mind are always expressed in words. He may not actually feel this, but as the Zohar explains, there is always a movement, however subtle.
Many people experience very strong mental distractions while they are trying to pray.
These can be immoral fantasies or even thoughts about idolatrous worship. There are even cases where people see vivid images of idolatrous objects or else they experience overwhelming temptations the very moment they stand up to pray. They try to push the thoughts out of their minds by tossing their heads from side to side. But the harder they try the more the thoughts press in. This is in the nature of thoughts like these.