Thanks everyone for your responses! The good news is that I read some more Piketty today and I seem to be retaining it easier, so I think Kepler is spot on about having to 'gear up' for different kinds of intellectual challenges. It's been a while since I've done such dense reading.
As for what I do with my time, now that my rental properties are all renovated & rented out, they are basically on autopilot. I have a property manager since our properties are in Michigan and my husband and I live in NYC, so the day-to-day management stuff is all taken care of.
So, now, I take 4-5 yoga classes a week, mystery shop part time (about 10-15 hours a week, usually; it's a fun way to dine out and do stuff touristy stuff for free), and help out a friend who is a dog walker whenever she needs help. I used to volunteer at the ASPCA, where I got my first dog, but then I fell for the dog who is now our second dog, and my husband and I agreed that I can't volunteer in places where I could end up with more pets (we live in a studio apartment).
Since then, I've volunteered with a program that teaches gardening to school kids, but it's seasonal (only when the weather is nice, and no summer).
Even when I was volunteering a lot at the animal shelter (which I definitely preferred to the kids's program), and when I ran my friend's dog walking business for all of February when she was out of town, I still felt like I wasn't using my brain the way I did when I was working.
I think I need to start doing more equity research on my own time-our money that isn't in real estate is mostly in mutual funds now, but I have a small 'fun money' stock trading account that I should spend more time on-I miss doing that kind of research.
I love to cook & I do a lot of cooking (and preserving in the summer when our CSA is in full swing). I also love to sew, but my sewing machine has been broken for a while- finally ordered the parts for it last week and fixed it today.
I think I need to get off my butt and start doing more of the stuff that I love, and challenging my brain-like more stock research, sewing, and research on indoor gardening (I have some plants but I'd love to have more). I studied Japanese in college & I love learning languages, so French lessons will hopefully force me to expand my brain that way once again. I do have some anxiety & depression (have for over 10 years, so not ER related), but I am on meds to treat that and see my dr every few months to make sure the dosage is okay.
Thank you for inspiring me and for the encouragement!