Effort to stay there is called practice. Yoga Sutra 1.13 RecitationAudio Recitation by D.C. Rao, PhD
tatra there sthitau the locative form of sthiti, stability yatnah effort abhyāsaḥ practice
Patanjali's instruction brings us back to the core element of practice: making the effort to remain steady in an internal focus.
You must find a support for the mind before you withdraw it from the external world.
Sutra 1.12 stated that through practice and dispassion we can attain mastery over the modifications of the mind. Now the author defines practice in greater detail.
Self-effort is the main characteristic of practice: no practice can ever be done unless you do it. That is why Patanjali says that practice means making an effort to stay there (tatra). The content hidden behind this word “there” is the most important part of the practice. "There" refers to the higher goal and purpose of life. In other words, employing all the means and resources—internal and external— to attend to the main goal of life without wasting your time and energy on anything else is called "practice."
This presupposes that you already know what the goal and purpose of life is. Without this knowledge, despite your sincere desire to do your practice, you float aimlessly. To undertake the kind of practice defined here by Patanjali you have to have a clear idea where you want to go, what you want to accomplish, and the central theme of your search. In short, what is your goal? Focusing your mind on that goal implies that you have already gotten a clear glimpse of it before you begin your practice. Only then can you make your mind stay focused on that goal.
In the journey of life, this is where most people err. They start the journey without knowing where they are going. They work hard, get exhausted, and then complain that they have reached nowhere. When you ask them “Where do you want to go?” they often reply “I don’t know.” This is what happens in the spiritual journey too. Patanjali’s approach to yoga requires you to find an object on which you can focus your mind. Without that focal point you will not be successful in withdrawing the scattered forces of your mind from the external world. Even if somehow you do succeed in withdrawing your mind from the external world, it will begin to wander because the mind does not know how to stay in one place without support.
You must find a support for the mind before you withdraw it from the external world. But be careful. The mind is expert in identifying itself with the objects of the world. If there are no worldly objects with which to identify, then it identifies with its own thought processes. If you do not provide any object for it, then for a brief time it will identify itself with nothingness (śhūnya). Soon it will get bored with that nothingness, and when that happens, the crafty aspect of the mind will come forward to fill the void with imaginary objects, fooling you into believing that you are having a spiritual experience. And if you randomly choose an object and assign it to the mind as a point of focus, you run the risk of tainting the mind with the intrinsic qualities and characteristics of that object. Therefore selection of the object on which to focus your mind is extremely important. This is why it is imperative that you receive guidance from an experienced teacher rather than waste your time experimenting with various objects of concentration.