One constraint that everyone has is working memory capacity. Or in other words, how many things you can remember at any one point in time. While there are individual differences in this, another aspect turns out to be more important: chunking.
Chess, Guitar Hero, Konami Code, Scrabble
Chase, W. G., & Ericsson, K. A. (1982). Skill and working memory. In G. H. Bower (Ed.), The Psychology of Learning and Motivation (Vol. 16, pp. 1-58). New York: Academic Press.
Chase, W. G., & Simon, H. A. (1973). Perception in chess. Cognitive Psychology, 4, 55-81.
Miller, George A. (1956). The magical number seven, plus or minus two: some limits on our capacity for processing information. Psychological Review, 63, 81-97.