Yoga is the science of Psycho-engineering. Just as physical sciences and technologies involve kinetic and potential energies for their operation, similarly science of psycho-engineering and maantrika technology developed in ancient India was based on Bhaavanaa Sanskaara or psychic energy. Yogadarshan teaches us as to how to pool the psychic energy and utilize it in achieving various siddhis or divine powers. Yoga enables one to command over one's mental functions or processes. It helps us to develop a particular type of feeling suited to one's life. The present book is a humble attempt to delve deep into the various psychological concepts dealt with in Yogadarshan and to find out the relevance of psychotherapy available in Yogadarshan in the treatment of present day psychological disorders distressing the humanity at large.