Energy is considered eternal; it never dies and this concept plays an important role in magic because magic is simply, energy subjected for a unique purpose. Well, that can be further decided that whether it's a positive or negative purpose that leads to two different kinds of energy that is positive and negative.
Now a question may arise "from where does the the practitioners get energy?" Well the answer for this varies from the personality and nature of person, as we see that energy is not just bounded or limited to several extent, it's present everywhere. If a person is much more attached to nature he/she can attain energy from nature, this the reason why many people feel good after they come from a morning walk in a park.
Now in yoga, what we do is the same concept and I consider it as revealing one's own energy and reviving it. We, in today's world, lose our natural level of energy. So friends, now I will end my article. I hope you raise your energy level and become a source of positive energy for others.