Question

Which lines from the poem express the view that life is too short and we should enjoy it while we can?

Answer 1

Lines 5, 6, 7, & 8  all express life is too short and we should enjoy it while we can. The lines all under those might also go with life is too short feeling.

Answer 2

I believe the answer is: Lines 5, 6, 7, & 8

Now, of my three score years and ten, - could be interpreted as years gone by without the author realising it.

Twenty will not come again - Could be perceived that you cannot reverted to your prime years

And take from seventy springs a score,

It only leaves me fifty more. - could be perceived as an advocate to live your life to the fullest.