When trying to make health and fitness changes to your life, the most important thing to know is that consistency is key. It's important to make a plan and stick to that plan.
Set Goals.
First, set your long term goal which is your ultimate goal. Your ultimate goal could be to fit into an old pair of pants, or to have a healthier diet for the rest of your life. Whatever your long term goals are you'll need to set short term goals to help you get there. A short term goal may be to start exercising or a grocery store run to buy healthier foods. Everything should be planned. Then plan out how to meet your short term goals, like making a grocery list before going to the grocery store.
Be realistic.
It is important that you keep it real with yourself. For instance, if I haven't worked out for much of my life then I'm not going to make a short term goal to run a marathon. Make sure all of your goals are attainable, otherwise you won't be consistent because it's just too hard.
Take things slow.
It's okay to take things slow. Don't worry about anyone else's pace but your own. It's important to crawl before you walk. For example, try illuminating a few unhealthy foods instead of illuminating them all at the same time. Do it this way so that the chances of you sticking it out are greater.
Lifestyle.
For me, being healthy and staying fit is worth a lifestyle change. I want to be as healthy as possible as I grow older. Being healthy and staying fit can help reduce and sometimes prevent illness like diabetes, heart disease, stroke, high blood pressure, colon cancer, and obesity.
Make a plan that is attainable that way you can be consistent, and remember starting off slow is okay. Your future depends on it!