In this octave from Sonnet VII by John Milton, how does the speaker feel about having not yet created a great body of work?

The speaker is worried about having not yet created a great body of work in this poem. He says that he is almost a man, 23-years-old, and that he still hasn't achieved anything important in his life. He is worried that it may be too late for him to fulfill his goals, because, according to his words, he has grown too old.