I'm glad you are writing about this. One kind of constructive envy--if felt and not acted out--is the envy of children. I am in menopause, let's say and my daughter is 20 years old. She is gorgeous and seems to have the world in front of her. She has had an easier and more fulfilling and less traumatic childhood than I did. I felt envious and then I felt of course, how could I not? But because I have loved and love her, my love is stronger. And because I knew my envy it did't strangle me or her.

It's not the most common or acceptable thing to admit.