Mind

When a thought moves, simply recognize the thinker. 
The thinking then dissolves. 

No matter what the thought is about, the thinking and the thinker are empty. A thought in itself is not made of any concrete substance; it is simply an empty thought movement. By recognizing the empty essence in a thought, it vanishes like a bubble in water. 

That is how to deal with any particular present thought at hand. Once you know how to let the present thought dissolve, any subsequent thought can be dealt with in exactly the same way, as simply another present thought. 

But if we get involved in the thought, thinking of what is being thought of, and continue it, then there is no end.

It is only our thinking that propels us or forces us into further samsaric existence. As long as we get caught up in our own thinking, samsara doesn’t stop.

- Tulku Urgyen Rinpoche