I have spent my days stringing and unstringing my instrument, while the song I came to sing remains unsung.

Rabindranath Tagore (1861-1941) Indian Bengali poet, philosopher [a.k.a. Rabi Thakur, Kabiguru]

“Waiting,” Gitanjali (1913)

Alt trans:
"The song I came to sing
remains unsung to this day.
I have spent my days in stringing
and in unstringing my instrument."

"The song that I came to sing remains unsung to this day,
I have spent my days in stringing and unstringing my instrument."

Sometimes titled "Song Unsung"

Full text.