While abhyasa and vairagya are opposite terms - with abhyasa referring to a "never give up" attitude and vairagya about a "letting go" attitude - they are the core principles that support a yogi's efforts at mastering his/her body, mind and soul. While abhyasa takes the yogi toward perfection, vairagya helps the yogi remain undisturbed to attractions of the world, thereby complementing the efforts of practice. A perfect balance of these two helps the yogi make such spiritual progress.
Abhyasa is not just limited to yogic practices such as asana, pranayama and dhyana, but involves one's day-to-day activities. The more focused the yogi is in every action, the quicker will be the spiritual progress.