Most of the time it is hard for us to continue on a particular task or activity for the main reason of, none the less we are tired. Often it is a habit of very lucky individuals to be gifted of—internal motivation, they are good at pushing themselves to their limits on their own. 

Most of our energy comes from within, physically it is very important, and for the lucky ones or I must say to a person who had been exposed to a lot of influences that drive him to be the best he can be. 

It is in our internal circuitry that is—our minds, second to our hearts.