This Seth quote reminds me of Lazaris' manifestation model in which we all have three "tools of manifestation" (desire, imagination, expectation) that we use to shape six "raw materials" (attitudes, beliefs, thoughts, feelings, choices, decisions) into moments of physical experience. Clearly, "what we concentrate on" is a foundational basis of our desire, imagination, expectation, attitudes, beliefs, thoughts, feelings, choices and decisions.
“You get what you concentrate upon, and your beliefs are largely responsible for those areas in which you concentrate.
“There are no magical methods, only natural ones that you use all of the time, although in some cases you use them for beliefs that you take for truths, when instead they are quite defective assumptions.
“Your experience will follow your concentration and belief and expectation. The mind is a great discriminator. It can use its reasoning to bring about almost any possible experience within your framework.”
(The Magical Approach: Seth Speaks About The Art Of Creative Living, Session Seven)