Yoga enables you to gain mastery over the subtle prana that disturbs the mind. Suppose that the mind is a covering and the covering mind is made of thoughts—like a screen woven with threads, as in a veil.
If you want to take away the veil, what will you do? You start pulling out thread after thread. If you pull out all the threads, what happens? There is no cloth to cover.
The mind is not just something by itself, it is woven by the thoughts. Meditation pulls off the thoughts one after the other. When all the thoughts are pulled out there is no mind at all.