Albert Barnes Commentary Psalms 89:45

"The days of his youth hast thou shortened: Thou hast covered him with shame. Selah" — Psalms 89:45 (ASV)

The days of his youth you have shortened - This does not mean that he had shortened his life, but that he had abbreviated the period of his vigor, his hope, and his prosperity. Instead of extending these and prolonging them into advancing years, he had, by calamities, disappointments, reverses, and troubles, as it were, abridged them.

No such youthful vigor, no such youthful hope now remained. The feelings of age—the cutting off from the world—had come suddenly upon him, even before he had reached the season when this might be expected to occur. Though at a time of life and in circumstances when he might have hoped for a longer continuance of that youthful vigor, he had suddenly been brought into the sad condition of an old man.

You have covered him with shame - You have clothed him with shame or disgrace. Everything in his circumstances and in his appearance indicates shame and disgrace, and the divine displeasure.