You'll depend on your friend to understand your deepest, darkest emotions and fears, and to put them into words for you. But they won't be able to understand you very well at that level, which will be frustrating for you both. The profound feelings and experiences that drive you, the ones that have shaped the person you are today, just won't be accessible to your buddy, try as they might to understand you.
They might try to put your insecurities or desires into words and fail abysmally, which will upset both of you; friends are supposed to be able to understand each other at this level, aren't they? But this sense of understanding will elude you both. Try to communicate in a careful, patient way. Develop your own ways to put your most profound feelings into words, rather than relying on your friend to do it for you.