Twilight's paranoia, OCD, and obsession with Friendship is going way over the line-- She can't think straight, she can't understand her surrounding, and she ends up making things worse for others instead of better.

She is then persuaded to see a doctor to help her deal with her problems, (In relations to past Friendship is Failure stories) and reflect on different perspectives and aspects of how life does not truly revolve around Friendship alone.

Lessons:

-There are times when you SHOULD try and help, and times when you should STEP BACK.
-Trying to force change on someone who doesn't want to change only make things worse, not better.
-Sometimes, no matter how hard you try and help or how much you want to... there is nothing you can do.