One thing I've found that I can do that I really enjoy is rereading my own writing, earlier stories and novels especially. It induces mental time travel, the same way certain songs you hear on the radio do ... the whole thing returns, an eerie feeling that I'm sure you've experienced.
Philip K. DickBarefoot conducts his seminars on his houseboat in Sausalito. It costs a hundred dollars to find out why we are on this Earth. You also get a sandwich, but I wasn't hungry that day. John Lennon had just been killed and I think I know why we are on this Earth; it's to find out that what you love the most will be taken away from you, probably due to an error in high places rather than by design.
Philip K. Dick