I totally agree.
You can not jugde a person if you have not walked a mile in their shoes. That is right. I also feel jealousy now and then (but not as I don't wish them their happiness) for other people, but often when you come someone Close and they open up, there has been other pain or worries that you did not see.

So we sometimes envy the beatiful "chocolate paper" or the box is kept within, from our idealised belief of what it contains, but inside it may have a bitter taste.
So we are just comparing ourselves with someones "best" circumstances. Everyone has a ups and downs.

And your future life is not the same as what has been before.

Everyday something special and fantastic can happen.
As Another wisdom Word, it is not about how things are, it is about how you take it

Easy to say I know, but you are definitively not alone with these thoughts.

And when feeling bad. Think that OK, at least I know what I dont want in my life, I dont like missing these things. Then I know the opposite as well, I know what I do want! and if you are fortunate to know what you want, focus on that and you will get it.