meditation can lead to mental instability, it does sometimes. The mind is a creature of habit and reputation. Do not dwell on what you might call bad thoughts. Untie your boat. Don't be like those drunkards, untieyour boat. If i am then don't give so much emphasis on meditation. I'll tell you what is to be done practically to purify the mind. One monk in utracanput said nicely: samadi, t asane martmaji sartekachit shut hona saapquaic minit mi samadi lagarding. That one he says mitata ra socate that one is called a hypocrite.