In Yoga, as in every great or serious human effort, there is always bound to be an abundance of adverse interventions and unfavourable circumstances which have to be overcome. To give them too great an importance increases their importance and their power to multiply themselves, gives them, as it were, confidence in themselves and the habit of coming. To face them with equanimity – if one cannot manage a cheerful persistence against them of confident and resolute will – diminishes on the contrary their importance and effect and in the end, though not at once, gets rid of their persistence and recurrence.
Ref: Letters on Yoga – IV