So I just had a random thought that I wanted to see was right or not. I have a pretty good friend who is an ENFJ (confirmed by legit test :P), and one day she told me that the main reason that she is an extravert is due to the fact that, when she is alone, she often reflects upon her failures in life. This is partially due to the fact that, when she's with other people, she has something else to focus her attention to - her feeling is allowed to travel outward, through her primary function, as opposed to being forced inward, and therefore moving into her primary shadow function, Fi.
As an INFP, and therefore having the same function order as her but flipped in orientation, I often feel the same thing when I am around too many people for a long period of time. I often begin questioning my own accomplishments when hanging around people who like to flaunt theirs - why don't I do this, or that? I can be most alone, deep inside my negativity, when I am surrounded by people, because my negative Fe is feeding into my Fi and making me feel badly.
Now, obviously, I'm not always sad to be around others - usually it makes me really happy, depending on who it is and how many there are of them :P. I'm sure this applies for my friend as well - she doesn't always get depressed when she's alone. But is it the fact that, when F types are out of our preferred element, we will begin relying on our "shadow" feeling function? And through that, we feed into our own negativity about ourselves, by using the function in a negative way? You see, INFPs and ENFJs actually have each other's dominant function as their dominant shadow function - INFPs have 5th place Fe, and ENFJs have 5th place Fi.
So that's basically what I'm asking - do other INFPs and ENFJs sometimes feel depressed when they are forced out of their element? F
EDIT: Forgot to add, this also applies to ISFPs and ESFJs as well.