Our imaginations are strong as children. Sometimes they get shoved aside these imaginations. They get dusty and mildewed with age. The imagination is a muscle that has to be put to use or it shrivels.
I don't think I could play a character that I couldn't relate to somehow. I'm not unfamiliar with frustration anger shame helplessness and a load of other emotions that make up our psycho-soup. I try to focus on that frustration that sense of unfairness and multiply it.