Will is a power of mind that can make one do something difficult, overcome any hurdle and achieve something great. The poet in the poem ‘If’ advises us to carry on even after the parts of our body stop functioning due to old age or any ailment. The power of will would force our body to work.

If you can force your heart and nerve and sinew
    To serve your turn long after they are gone,   
And so hold on when there is nothing in you
    Except the Will which says to them: ‘Hold on

It is important to force our body to serve us for a longer period if we have to succeed in our mission in this short lifespan. World’s greatest achievers have often overcome the difficulties on their way of life by their power of Will.