That's a good place to be in your career. Learning complex subjects is much more about quality than quantity (there was a recent HN article about effortful repetition, rather than mere repeated exposure, being the trick). So even if you want to really learn this stuff, learning to give your brain a break might be just what you need to both process the information and find pleasure in it.
Meditation is for real. But you might also be in danger of approaching it as "a task"—I did. What I do when I sense that my body just needs to relax, now, is I lay on a yoga mat on the floor and sort of stretch without trying and gradually feel my breath and slow down. Sometimes it becomes a real work out, but I never do it with that intention. Just a suggestion.