If your previous attempts to get in shape have been derailed by an injury or an inexplicable pain, you've got to address it before you can expect to push yourself. Make an appointment with a chiropractor or physical therapist, and treat their rehab guidelines as your most important workout. From shin splints to IT band tightness to neck pain, there's a surprising amount of improvement you can make with proper stretching, foam rolling, and rehabilitative strength training. Ask your health practitioner when you should expect to see significant improvements by, sign up for a fitness class or race after that date, and make self-care your job.