I find that my intuition does its best work when I am more connected to the world. I need to fill my mind first with concrete objects, facts, data, ideas, and the intuition works to fill in the gaps and show me the right direction to go in. If I leave my intuition to run wild, which seems to happen when I am stressed and withdrawn from the world, it starts to take on a life of its own, and the images and ideas it throws at me tend to be tragically blown out of proportion and somewhat morbid, albeit very real. Fortunately I am learning more and more to catch myself and keep myself out of this trap, but it's not always easy and feels unnatural most of the time.
I have an unhealthy INFP friend who is extremely paranoid. She recently failed to graduate from a Masters program because according to her all the faculty at the university were in this huge conspiracy to fail her. She was reading all kinds of stuff between the lines and it didn't help that English was her second language. I went through her e-mail exchanges with her professors and counsellors which were all very normal, and asked a relative who is also a professor for a second opinion on her paper. The answer I got was that her paper wasn't sufficient to pass, and she needed a lot of help from her professors if she was going to graduate.
I don't know many INFPs but the ones I do know seem to have a harder time then the rest in taking a step back and looking at themselves critically. In extreme cases like that of my friend, intuition is really causing them to sabotage their career..