How does one realise when one has crossed the line between wishing one was like another person and envying that person?

I ask because once upon a time there were three friends living not too far apart from one another. Well, eventually one relocated and another went in search of greener pasture for a while. Eventually, the one in search of greener pasture returned and as you might have guessed, went to say hi to the relocated friend without so much as a knock at the door of the friend next door.

I guess when it comes right down to it, you could say a choice has been made but what is the friend next door to feel? Envy or wishful thinking?

Either ways, I just thought to leave a food for thought even as I call it a day and snuggle up in my blanket. *sweet dreams*