It seems like OP has piled intellectually intense hobbies (learning a foreign language, reading "complex" books) on top of a intellectually challenging career.

It seems like OP has piled intellectually intense hobbies (learning a foreign language, reading "complex" books) on top of a intellectually challenging career. Thats not going to work for most people, just like most people cant spend 12 hours a day on their career. So while maybe watching TV is a little too passive, there are lots of in between activities that might be useful: cooking, gardening, meditating, things that are reasonably mindful, but work different mental muscles than thinking about algorithms or data structures.