Sutra 1.2 Yogah Citta Vritti Nirodah - Yoga is the stilling of the fluctuations of the mind (so that the self can dwell in its own splendor).
Sutra 1.12 Both practice (abhyasa) and non-reaction (vairgya) are required to still the patterning of consciousness.
Sutra 1.13 Practice is the sustained effort to rest in that stillness.
Obstacles (Kleshas) to this process
II -3. Avidyasmita-raga-dvesabhinivesah klesah
Dharana - concentration
Dhyana - meditation