"when the keepers of the house tremble, and the strong men stoop, when the grinders cease because they are few, and those looking through the windows grow dim;" NIV translation
We cannot stop the passage of time and the strength of our youth will fade. The things that we once did with ease become a chore. It does not matter how much you take care of this earthly physical body; in the end it will fail you. In our world today, there is much emphasis on the physical training of our bodies and staying in shape. This is good for us but some people make this like an idol in their lives.
Our world is full of the hustle and bustle of everyday life. People going to and fro to get ahead in this world. A part of this aging is the fact that we have to move slower. It often seems like we are falling behind and being left in the dust by the pace of the world around us.
In our youth, many will work long hours (getting up with the birds) to do more and more. In our golden years, we may still get up with the first sound of the birds but our strength (songs) is gone and we cannot keep up this earthly pace anymore. Many will spend their youth running as fast as they can to get ahead in this world but, in the end, the world will pass us all by.
"when people are afraid of heights and of dangers in the streets; when the almond tree blossoms and the grasshopper drags itself along and desire no longer is stirred. Then people go to their eternal home and mourners go about the streets." NIV translation
Without Christ in our golden years, fear creeps in and the courage of our youth fades with the time. We all have the feeling of invincibility while we are young but, in the end, we are all subject to physical death. Without Christ, the thought of death will bring stress and fear but, with the prospect of joining our Lord forever, we do not have the fear.