In this poem, Housman shows a "carpe diem" attitude towards life. He realizes that life is short and, because of that, he believes that we should try to live life to the fullest. We should go out and enjoy everything life has to offer because life will end too soon (even if we live to an old age).
In the poem, Housman uses the idea of looking at cherry blossoms to stand in for experiencing everything life has to offer. He talks about how even fifty more years of life is not enough to "look at things in bloom" -- that is, to do all the things that he would like to do. Therefore, he says, he will go out and do as much as he can.
As this shows, Housman's attitude towards life in this poem is that life is short and that people should, therefore, grab it with both hands and enjoy it while they can.