Yoga citta vritti nirodhah - Control of the mental fluctuations is yoga.
It's so simple and to the point. The sutras start off by broadly stating that yoga is the present moment. But the second sutra describes a means to experience it.
If you ever wondered about what Yoga is all about, that is it. Science today shows that the ability to do exactly that is the key to living well overall. To master it within our own means simply takes time and practice.
"Yoga teaches us to cure what need not be endured, and to endure what cannot be cured."