One of the things that teaching summer school has made me very aware of is how accustomed I've become to the usual rhythms of the semester -- there's the semester-long rhthym of energy & enthusiasm, followed by a kind of settling down, and a midterm lagging of energy, then a renewed focus until the chaos of the last couple weeks -- for both me and the students. And there's also the week's rhythm -- which for me generally involves two intense teaching days, usually T/Th, with M/W being devoted to meetings, class prep, and research. Fridays are traditionally my day off, with writing and grading on the weekend. There are variations due to schedule changes and special events, but I've become very used to the on-off energy cycle, which suits me well. I'm comfortable performing in the classroom and dealing with students, but I'm essentially an introvert, so I need time to recharge after working with other people all day. Having a day inbetween teaching days gives me time to process what's going on in class and plan for the next day at a deeper, energetic kind of level -- not just reviewing the material and making handouts, but a different sort of planning that happens subconsciously but makes possible those spontaneous decisions that often produce great classes.
But in summer session, it's MTWH -- so the top-level prepping is manageable, but the deeper processing isn't happening -- nor the recharging. By Friday, I'm really wiped out and don't want to talk to anyone. Then I act like a hermit all weekend to make the next week possible. I'm not complaining -- I needed the extra pay (paltry though it be) and there's only one week left -- I can do anything for five weeks. But it's made me extra grateful for the schedule I'm usually able to work out, to fit all my classes into two or sometimes three long days. Those days inbetween are really important for my teaching, in ways I hadn't fully realized before.