Good luck understanding me because I sure as hell have a hard time at that. My thoughts about myself are constantly in flux.
Your assumption that I am original is correct and it constantly leads me to feeling like an outcast which leads to a lot of negative thoughts and feelings, sometimes to the point where I consider suicide as a realistic option. But on the other hand I am very capable of creating things that other people enjoy such as music and art.
My creativity, I think, is a function of nostalgia combined with in the moment sensations. Nostalgia gives me a strong motivation to recapture distant vague positive feelings/memories. What I create today will then lead to future feelings of nostalgia and the cycle repeats. This, I believe, is the foundation of my creative process. My end products may seem negative to outsiders but to me they represent peace and happiness. My originality is a combination of feelings, thoughts, and memories. I hope this helps, if not I am more than willing to explain further but I think that I may not be someone who represents the majority of ISFPs and therefore my words may be tainted.