"Yesterday when I was young" was Roy's biggest hit; his only Top 40 hit.
It was originally a French song, "Hier encore" written by Charles Aznavour.
Mickey Mantle asked Roy to perform it at his funeral.
According to wikipedia:
"The English-language lyrics, written by
Herbert Kretzmer, tell of a man reflecting on his life. He recounts how he had wasted his youth on self-centered pursuits, and that, now that he is older, he will not be able to do all that he had planned; this implies that he may be close to his impending death."
Warning: This is a tear jerker.