If you eat a lot of starchy foods, introduce a vegetable once a week, then twice a week, and then three times a week. Slowly fill your diet with new flavors. By the time you're ready to let go of whatever it is you want to let go of, you've got a full menu.
Exercise helps me with stress. It changes your brain chemistry. I turn to Ashtanga yoga when I feel the need to relax. I love it, but it's not right for everybody. It's taught to you a little bit at a time, according to your body type and your strength. That keeps things challenging.
By learning about my body and making small, subtle changes, I find out what I enjoy and what is effective. I'm always finessing: adjusting my diet and my workouts. You have to figure out which exercises are fun and interesting and stimulate your brain - or else you'll never keep at them.