Why does my blood thus muster to my heart, and dispossessing all my other parts of necessary fitness?

Why does my blood thus muster to my heart,Making both it unable for itself,And dispossessing all my other partsOf necessary fitness?

It will have blood, they say; blood will have blood.

Thus conscience does make cowards of us all.

Stiffen the sinews, summon up the blood.

Teach thy necessity to reason thus; There is no virtue like necessity