For us INFJs who have complex and puzzling mind, I'd strongly suggest meditation. Meditation is the key to calm the mind. My monk friend used to use this analogy: he shook a bottle of water, all the bubbles and the swirling water is like our mind. Meditation is like holding it still afterward, so that all the bubbles disappear and we can see the water more clearly. I've tried it and so far, it's the only thing that can really keep me sane.