Charles Ellicott Commentary Psalms 90:10

"The days of our years are threescore years and ten, Or even by reason of strength fourscore years; Yet is their pride but labor and sorrow; For it is soon gone, and we fly away." — Psalms 90:10 (ASV)

Yet is their strength ... —The Septuagint (and the Vulgate likewise) seems to have had a slightly different reading, which makes much better sense: Yet their additional years are but labour and sorrow. The old man has no reason to congratulate himself on passing the ordinary limit of life.

For it is soon cut off. —This hardly seems to provide, as it claims to do, a reason for the fact that the prolongation of life beyond its ordinary limit brings trouble and sorrow, and we are compelled to see if the words can convey a different meaning. Literally, the clause is, for (or thus) passes haste, and we fly away (like a bird), which may be rendered, thus there comes a haste that we may fly away; that is, even though we may have prayed for an extension of life, it brings with it such weariness that we long at last to escape—a fact sufficiently true to experience.

“Yet are these feet, whose strengthless stay is numb,
Unable to support this lump of clay,
Swift winged with desire to get a grave.”

SHAKSPEARE.