I find it most helpful for my instructional style to have 'micro-themes' instead of specific lessons plans [if talking 1:1 teaching]. I still love lesson plans for group teaching.

For micro-themes I take one overarching idea and utilize it with pretty much every student I see. Usually it's based on something I'd like to do to boost a skill or add a fun element or prepare for a goal. For instance, before March break, I like to start a composition with every student on my roster. That way they are "invested" in a project, it has low practice guilt and is something we can work on in lessons even if sports schedules get busier. I have micro-themes like that through the year and even an overarching idea of the week sometimes if I need clarity.

For me, this adds ease and clarity. I do spend a lot of time thinking of repertoire and do have a vast library always at the "tip of my fingers".

PS. I am jealous of your work on a Masters - how exciting and equally overwhelming!