Dig a nail of your index finger into the cuticle of the thumb of the same hand until it becomes quite painful. Concentrate on the pain: it is a physical reflection of the suffering you are going through spiritually. Ease the pressure only when the cruel though has gone.

Repeat this as many times as necessary until the though has left you, even if this means digging your fingernail into your thumb over and over. Each time, it will take longer for the cruel though to return, and eventually it will disappear altogether, so long as you do not fail to perform the exercise every time it comes to mind.