Sentence:  Life is too difficult. O. Greenbaum, H. Knape, T. Kornflower, J. Davenport, all would agree that “Life is but the span from womb to tomb; a sigh, a smile; a chill, a fever; a throe of pain, a spasm of volupty: then a gasping for breath, and the comedy is over, the song is ended, <WSD>ring down the curtain</WSD>, the clown is dead.” 
Meaning of the word marked with <WSD> tags:  To mark the end of something.