Seth Godin's phrase of choice is "it might not work." If you view this as pessimistic let me tell you why this is a great expression to come to terms with and ultimately put to use pursuing your passion:
Rather than this sentence expressing the possibility of failure, it's really just stating the worst that can happen. It might not work. That's it. That's the worst possible outcome of trying something new and going out on a limb. When you look at it that way, this little saying becomes our best friend.
"What happens if I try X?"
"Well, it might not work."
"Let's find out."
That's about the extent you should let your mind get in the way of following a passionate course of action to make meaningful art, whether it's painting with acrylics or securing a multi-million dollar deal.