Please clearly understand that when the mind is still, it’s in its natural, normal state.
As soon as the mind moves, it becomes conditioned (sankhāra). When the mind likes something, it becomes conditioned. When not-liking arises, it becomes conditioned. The desire to move here and there arises from conditioning.
If our awareness doesn’t keep pace with these mental proliferations as they occur, the mind will chase after them and be conditioned by them. Whenever the mind moves, at that moment, it becomes a conventional reality.
So the Buddha taught us to contemplate these wavering conditions of the mind.