A Vineyard & An Older Son

It was striking -- though I couldn't remember ever thinking it before: The older son in the parable of the prodigal son and the workers who were higher at the beginning of the day in the parable of the vineyard -- they were the same.
The older son was self-righteous, angry at his Father for giving his little brother anything.
The morning workers were self-righteous, angry at the Master for giving those hired later the same wages.
Why? It didn't cost the older son or the workers anything. They both still got everything they had been promised. But we are just like them. Even if we don't lose anything, we are still unhappy when others get more than we do or get more than we think they deserve.
How can we respond to God's great generosity this way in light of all He has given?