There is an eternal Will working out Its incalculable purpose. Man can align himself to this eternal Will or work at cross-purposes to It. Yet in either case, ultimately the eternal Will is bound to prevail. We can only choose the path towards that.
"... yoga itself has evolved and changed as humanity has evolved and changed. For each Age there is a yoga appropriate to the Age. It is in this context that we try to trace in brief the evolution of various yogic systems."
Pain is the signature of Ignorance. But what compelled the immortal soul to become subject to death and Ignorance? Well, its own unique choice since thus alone it could arrive at its fullest blossoming.