So basically hobbies and travel... My problem - my hobbies is what my friends see as a "work" (and I identify it as a work as well). Traveling is alright (although it is plenty of work with whole family, which includes two kiddos) - but it gets old rather quickly (again, perhaps part of it the fact that it is family traveling, so entertaiment options are rather limited)... Perhaps kiddos get old enough I might re-discover traveling as a way to relax, but until then doing nothing makes me more anxious than just keep working. And these self-help/productivity book are just tools, just like "c# for dummies" books.
Anything that helps you feel relaxed and at ease.
I'm always super busy with work and side projects, but last December I went to Maui for 2 weeks and it was the best thing I did for myself: when I returned, all the things I had to do ("work") crept back in and I realized what it actually meant to be relaxed (because in this condition, I'm definitely anything but that).