1.2 Yoga is the cessation of movements in the consciousness
[Other interpretations:Yoga is the control of the modifications (gross and subtle thought patterns) of the mind field
The skill of yoga is demonstrated by the conscious non-operation of the vibrational modes of the mentoemotional energy.]
So this sutra is attempting to define the practice of yoga. Note that by ‘yoga’, this does not just mean ‘asana’ or postures (what we in the West think of as yoga), but the whole package of yogic practices. By practising the yamas and niyamas (more on that story later), by controlling the breath through pranayama, connecting the body and mind through asana practice, and through withdrawing the senses and meditating, then we can control the mind. By ‘control’, it means quietening, stilling, and regulation, rather than suppression or repression.
I think I prefer Iyengar’s interpretation here (the first one), as it is the most succinct. It does not attempt to state why quietening the mind is desirable, just that it is the goal of yogic practices. A noisy mind is definitely an issue for me, it’s a real conscious effort to slow things down and turn the volume down up there (and I’m not always successful). Once that happens, then it is easier to see and experience things as they really are, not our interpretation of them (which is often inaccurate).