2.21 The very existence of the seen is for the sake of the seer.
I find this sutra interesting because it's short, but covers a broad subject. Various branches of Vedic study have differing opinions on what the universe is, how it began and why we are here. Sanatana Dharma is the eternal order of the universe and is the proper name for the religion called Hinduism.
Hindu creation stories somewhat mirror those of Christianity. They believe that the universe runs in a pattern of cycles, each one smaller than the next. There is a measurement for the universal cycle: a Yuga. Brahma, the creator God, awakens from a slumber and the universe begins again, as if it were a new day, before he falls back into sleep at the end of his day.
In the beginning, the One was broken up into infinite divisions with the sole intent of experiencing itself. Eventually, these divisions begin to merge back into the whole as creation starts to fall asleep. Yoga speeds up what is be considered a natural process. Your soul will eventually merge back with everything, it just takes a longer.
Some say that enlightenment is reached at point of merger, but are still in the body. Thus, we are the seer, a part of the larger version of the universe experiencing itself. Our life purpose is simply to be a part of the larger experience. In my earlier posts, I compared the process of Yoga to untangling a ball of yarn. We can see how simple the master plan is the more we untangle that ball of string. When I say the world is already perfect, I mean that at its root level, there is nothing that needs to be done. We just think we need to make changes to it to satisfy our desire. So, if you never do any sort of Yoga, at least try to enjoy yourself as much as possible.