Energy!

Today I am realizing the importance of energy. I think what it comes down when u see successful people around. Look at those people, after hours of fight or political fight I can say, they go to bed early and ready next day for another day. They also enjoy sports etc. So I think basically how you spend energy, and kind of engery u got makes u a successful person. Today, I had big meeting. I fought against misconceptions, some stupid leaders etc. and now its it just 4 in afternoon and I am tired. I think having this huge amount of inner energy will help, but question is how do u gain it. If you can't then, atleast I should learn the art of spending it properly.