If you have some expectation, and you cannot get what you want, then the mind becomes bored. So, check your attitude. What idea do you have when you’re watching the defilement? If you have the right attitude and right view when watching the defilement, the defilement will slowly get weaker and weaker. But if the defilement gets stronger, then there is something wrong with the watching mind.
Actually, the most important thing is attitude. If the attitude is right, the object becomes more distant. Don’t expect the understanding to come – it only comes due to right conditions. If you have expectations, the right conditions cannot arise. When you don’t have any expectation, then wisdom can arise. If you want to understand, wisdom cannot come because they are opposites.
Just practice continuously, and be interested in the process, that’s enough. Don’t try to get something or expect something. If you know that there’s expectation, watch the expectation first.