Sometimes the mind may wonder about practice itself. For example, the mind may wander off into analyzing whether an object was noted effectly, or seq… - Mahasi Sayadaw

When one cultivates strong concentration by means of tranquility or insight meditation, the mind is no longer distracted by thoughts and other hindrances. Such pure concentration, continuously focused on an object for either tranquility or insight, is considered mental purification. A mind associated with such concentration is also purified of hindrances due to the power of the concentration.

One should keep oneself occupied all the time with wholesome deeds such as: learning, teaching, memorizing, reading, scrutinizing, and chanting the Buddhist scriptures; discharging the daily duties of a monk; discussing the Dhamma, only speaking about the Dhamma; giving or listening to Dhamma talks, and practicing asceticism.

Uncertainty about what is wholesome and unwholesome is called skeptical doubt (vicikiccha). It is considered a hindrance to liberation as it hinders the arising of discriminating knowledge. A person who has doubts about the wholesomeness and unwholesomeness of phenomena is unable to abandon what is unwholesome, develop what is wholesome, and escape the cycle of suffering.