Sentence:  For the bliss of the animals lies in this, that, on their lower level, they shadow the bliss of those—few at any moment on the earth—who do not "look before and after, and pine for what is not," but live in the holy carelessness of the <WSD>eternal now</WSD>. 
Meaning of the word marked with <WSD> tags:  The condition in which all reality is experienced in the present, with the past contained only in memory and the future only in anticipation or speculation.