Exertion is the Most Helpful Quality
In the Canki Sutta (MN 95), the Buddha explains to a knowledgeable Brahmin (a person of the the highest social class in traditional Hinduism) how someone can come to the definite conclusion that something is true. He explains that one must have conviction but wait to make the conclusion. Naturally, the Brahmin asks how one can can attain the truth, hoping to get a concrete answer from the Buddha.
The Buddha eventually answers the Brahmin's question: a person must purify themselves of the qualities of greed, aversion, and delusion in order to have a clear, unbiased mind that can understand the truth. However, the Brahmin is not satisfied at that and wishes to know the quality that is most helpful for accomplishing this task. The first quality that the Buddha gives is exertion, followed by qualities that support exertion.
The Century Dictionary defines exertion as “The act of exerting; the act of putting into motion or action; effort; a striving: as, an exertion of strength or power; an exertion of the limbs or of the mind.”
This is a helpful quality for success in almost any endeavor, including the cultivation of prajna (wisdom), dāna (generosity), and mettā (loving-kindness).
Because one makes an exertion, one finally attains the truth.
To exercise and make the body healthy, one must exert effort by taking time out of the day and working the muscles. To eat well, one must exert effort in finding, preparing, and consuming healthy food. To learn a new concept, one must push the mind beyond what it already knows.
In the meditation practice, this means actually practicing meditation. It's easy to watch a monk give a talk because it's a passive activity, unless you really put forth the effort to analyze the talk. To exert oneself in the meditation practice, it would be better to choose thirty minutes of meditation over hours of watching videos online of teachers giving talks.
It is easy to talk about doing something, but real progress arrives through exertion—putting that activity into motion even if it's difficult.