The discipline of a meditator is to become so watchful of the mind, so alert to the mind and its stupidities -- its hesitations, its tremblings, its vacillations -- to become so watchful that you are cut off.
That is the whole purpose of watching: watching cuts you off.
Watch anything in the mind, and you are cut off. Watching is a sword.
If a thought is moving in your mind, just watch it -- and suddenly you will see the thought is there, you are here, and there is no bridge left. Don't watch, and you become identified with the thought, you become it; watch, and you are not it. Mind possesses you because you have forgotten how to watch. Learn it.