1. Get out of the house. Get a desk at a co-working place - It's cheap enough, in most cities (in my small-ish, banking-obsessed city, I can still get a coworking non-reserved desk for $60/mo, and a permanently reserved desk for under $300, and it comes with free soda/coffee, so the effective cost is $0). You might even meet some freelance designers or programmers while doing it.
2. Create a schedule for the gym. If you can't seem to stick to a schedule to go to the gym, sign up for a multiple-week boot camp or a program through CrossFit - I've been able to keep to a gym schedule, but bootcamp and crossfit are both on my "todo" list for the next year"
3. Learn to cook. Just buy food and then figure out what to do with it. A few weeks back, I went to Costco and bought a 3lb bag of French Beans and a 5 lb bag of Broccoli on a whim. Then I had to figure out what to do with all of that before it went bad. Throw in some chicken, Google some random recipes, and figure shit out. Easy, quick, delicious, healthy meals.
Right now I still have my day job, though I've been making enough not to have that. But I enjoy my co-workers, and working in the industry, a good portion of my team does their own shit on the side, and it's a great group to learn from. And a few people I know who've gone out on their own have gotten co-working/part-time work space & started to focus more on fitness due to having more time available - All seem to be doing well, and haven't fallen into a laziness rut.