I knock unbidden once at every gate-- If sleeping, wake--if...

I knock unbidden once at every gate-- If sleeping, wake--if feasting, rise before I turn away--it is the hour of fate, And they who follow me reach every state Mortals desire, and conquer every foe Save death, but those who doubt of hesitate, Condemned to failure, penury and woe, Seek me in vain and uselessly implore, I answer not, and I return no more.