One thing that has helped me in several areas of life is the idea of small, deliberate changes that build on themselves. Here are a couple of examples, but it can apply to so many other things in life. Finances, for sure, but everyone here probably already knows that! :-)
Running: I started running on the day I graduated from college, using a "couch potato to 5K" plan I found online. It had me starting with running for something like one minute, walking for two, and repeating for 20 minutes or so. I wasn't overweight or out of shape (well, maybe I was more out of shape than I thought), but it was a big day when I got to 5 minutes of solid running. Since then, I have run two marathons, and I continue to run for an hour straight each time I go out.
Nutrition: You don't have to overhaul your diet overnight. You do have to realize that changing what you eat is not a temporary fix but a lifestyle change that needs to be permanent in order to have lasting effects. For some people diving in head first works best, but for others, changing just one thing at a time can make a big difference without making you feel deprived, and over the next few years, you'll find that your tastes change and your health improves. Start by just adding one vegetable a day to whatever your normal daily food intake is. Then add another one. Or a piece of fruit. Or a small handful of nuts. The healthy things will start to crowd out the unhealthy things, and before you know it, you'll be doing much better overall.
A little advice based on my profession:
When you go see a doctor, take with you a list of your health problems, surgeries you've had, medications you take, allergies, and family medical history. Also have some idea of how much you smoke or drink so you don't have to sit there and do the math when you're asked. Carry this list with you in your wallet (or wherever) at all times so it will already be with you if you ever have to go to the ER. (It's also helpful to give this list to your family or trusted friends so they can help if you're ever in a situation where you can't speak for yourself.) Even if you can remember the name of the one allergy you have on any given day, you may not be able to remember it when you're hurting and stressed, and you certainly won't be able to tell anyone if you're unconscious. Do not rely on the hospital or office computer system to "remember" all this stuff for you. Computer systems have downtime or simply malfunction, and even if everything is working fine, you'll save everyone a lot of time if you can just tell them. It's also good for healthcare staff to be able to confirm that whatever is in the computer is consistent with what you actually have. I've come across charts that contained medical problems or surgeries or allergies that the patient never had. Computer entry errors happen.
Do not pee right before you go see a doctor if there's even the remotest possibility you'll need to give a urine sample! You'll save yourself a lot of time!
Consider getting one of these: roadid.com It's a little rubber bracelet on which you can have them write your name, phone number of a loved one, medical history, allergies, etc. in case you are ever unconscious and in need of help. It was developed for cyclists, but I wear one all the time in case I get hit by a car while running, randomly pass out somewhere, have a medical problem while I'm traveling, etc. (The only time I have ever had to use it was when I locked myself out of my house and had to borrow a neighbor's phone to call my boyfriend to come home and let me in. I don't have his number memorized, thanks to my cell phone, which was inside the house, but it sure would have been necessary to know his number that day if I hadn't had it strapped to my wrist!)