Yep, you can take today off. I was like you in my first term, but eventually you nail down a really solid workflow for the week which will almost always give you a day off (other people allocate days differently, of course, but I do 3x days reading, 1x day planning, 2x days writing/proofing, which gives me a day off to wander to the library and get the books out for next week's essay etc). I'd highly recommend Grantchester or the Botanical Gardens, or even going for a wander down the Cam can be nice once you get out of town and into the countryside (approach Jesus Lock from town, turn right and walk past the Fort St George and the boathouses for over a mile).