That which is known as "meditation" is the act of sustaining an object of meditation and specific subjective aspects by repeatedly focusing your mind upon a virtuous object of meditation. The purpose of this is as follows. From beginningless time you have been under the control of your mind; your mind has not been under your control. Furthermore, your mind tended to be obscured by the afflictions and so forth. Thus meditation aims to bring this mind, which gives rise to all faults and flaws, under control and then it aims to make it servicable. Servicability means that you can direct your mind as you wish toward a virtuous object of meditation.
The Great Treatise on the Stages of the Path to Enlightenment, as translated by Chenmo Translation Committee (2000) p. 99