It happens in various random times. Mostly being inspiration to people in need. I find E2's to be the ones asking me for help most often.
My ENFJ E2 friend once called me during the lowest point in his life, he was blacking out, alcoholic, drug addicted...
Our conversation went something like this (paraphrased):
friend: Jay! How's everthing going dude! *something about his voice hinted to me that something was very wrong*
me: I'm fine, How're things going with you?
friend: oh... not very good
me: what's up?
friend: I'm blacking out etc, don't know what I want to do
me: well what's something you want to do in life?
friend: I want to help people
me: well, dude, you're in no position to help others right now... you can only give to others if you yourself have something to give.
friend: wow... you can only give to others if you have something to give. That makes perfect sense!
me: yeah man. You want to be a rockstar right? Well, every rockstar reaches rock bottom once they're thrown excess. You somehow managed to get all of that out of the way.
friend: I did!
me: So now that you know what its like to hit rock bottom, you've made your mistakes, its time to stand back up and make it happen.
He rose up, is now clean, acting on broadway, has a girlfriend who doesn't suck, and he put one of my lines as one of his favorite quotes on his facebook page . I felt moved that I was able to help someone in that way.