The nature of the gunas is to change. But the art is not to wait for such change, but to appeal to sattva. This is not accomplished necessarily by rejecting rajas and tamas, but by calling on sattva. One thinks, "I was feeling peace and balance before, so where did it go all of a sudden?" So water the flowers, not the weeds. Inspect the mind each morning. Do not go out without sattva. From the habit of sattva comes higher sattva (desire for spiritual practice), and from that comes a springboard into different samadhis.
You have to have the ability to go out into the woods and sit under a tree for 49 days, or spend forty days and forty nights in the wilderness There, one can really take the mind and ego to task.
It takes a great yearning, a great austerity, to realize the Truth.
Sri Krishna says that what is good starts as sour, and what is bad starts out as sweet. But the world has it backwards. We have beer trucks running up and down the roads delivering liquor to smokey bars for people to get drunk with, and then go home and beat their spouses or neglect their families, and society generally accepts this as good or normal. But these same people think that going home to meditate and study scripture, or to spend time with their spiritual teacher, is bad. Welcome to the topsy-turvey world of maya.
Whatever it is, there is something underlying name and form. You have to penetrate deep to find the essence. Like finding oil in sesame, patina in copper, butter in milk -- you have to work to get these subtle essences. This is what is considered sour in the beginning. It is called sadhana, spiritual practice.