>>149462 (OP)
Rest is really important.
I really love training, like I fuckin love going to the gym and seeing my buddies and pumping iron. I have to make myself take days off, though, because training every day will definitely set you back… you get sore, but more importantly, you get weak.
I have found that only training legs twice a week (one day for bar squats, another day for everything else - various machine presses, etc) actually gives me more gains than an every-other-day approach. Same with upper body. Really the only thing I do every gym session is abs, and that's to keep my back healthy more than anything.
Everybody is different, but for me personally, two days of legs and two days of upper body (big compound movements that hit multiple big muscles) and really giving it your all is much more effective than a half-ass daily workouts.
Rest days can include walks and biking - I usually do my cardio on "rest" days. Just no weights.
tl;dr: rest is just as important (if not more) than training.