Charlotte Mason lists Reason as one of her Twenty Principles: “We teach children, too, not to ‘lean (too confidently) to their own understanding’; because the function of reason is to give logical demonstration (a) of mathematical truth, (b) of an initial idea, accepted by the will. In the former case, reason is, practically, an infallible guide, but in the latter, it is not always a safe one; for, whether that idea be right or wrong, reason will confirm it by irrefragable proofs” (Charlotte Mason, Towards a Philosophy of Education xxxi).
“Reason” represents a lot of subjects, so practicing it daily isn’t hard. Math. Science. Logic. Latin. English Grammar. All of those require systematic thinking and organized work. These things need habitual practice in order to reach mastery.
This coming year, Micah will tackle thesis-writing, Virgil, Trig, and Physics while Josiah and Gideon work on essay-writing, Henle Latin 1, algebra and life sciences (astronomy and biology). But the goal of all that work is not the adding of specific knowledge. The large goal is to develop the ability to work through problems even if they look big or scary. In order to do that, we need lots and lots of practice.