Well, how come so few of us are able to make those changes?
Because change sucks, that's why. Nobody likes change. It's not fun and it's hard work. It is much easier to keep doing what you're doing, to stay on the path of least resistance. To settle. People get into a rut, it's human nature. We all do it, whether we like it or not.
A rut is just a grave with the ends kicked out.
How do we go about creating change, then? For starters, you need to WANT to do it. There needs to be an intrinsic motivation that says "It's time to make something happen." There can be an external stimulus, but in the end the motivation has to come from within you. No one else can tell you it's time to change...well, they can try, but it won't have any meaning to you until you are ready.
Change takes change, is a saying I like to use often. The first few weeks of a diet and exercise program is probably going to feel like shit if you've never done it before. You know what though? It gets easier. I swear to God. It becomes a new habit, a healthy habit.
You're ready to change now? Good. You're going to need some strategies. For starters, get with like-minded people. If the people you normally hang out with have only seen the inside of a gym on The Biggest Loser, then hang out with some different folks. Similarly, if your social circle revolves around trying out the newest buffet and sitting at a bar crushing beers a few nights a week, you might want to find a social group with some slightly better habits. "A's get with A's", as the saying goes. If you want to be successful, you need to surround yourself with successful people.
Make a plan. Whatever your goal is, planning will help. If its a health/fitness goal, seek some professional help. Talk to some of the trainers at your local gym and see what they can do for you. All it takes is a nudge in the right direction to get things going. Make your goals known, tell people what you have going on. If you want to deadlift 405 by Christmas, tell everyone on Facebook. Make it a public goal; you'll be much more motivated to make it happen then.
At the end of the day, you really just need to decide to make the change. It takes a while. Like I said, it's not easy. But you will be better off once you change that bad habit.
Form a good habit right now: go to the gym and pick up something heavy!