1. Feeling overwhelmed by stress
Since caveperson times, we've known excess stress lowers our immunity, boosts the risk of heart disease and generally makes us feel crummy. But now Elissa S. Epel, PhD, a professor of psychiatry at the University of California at San Francisco, has cell-level proof that too much stress triggers premature aging of the immune system. Mothers of chronically ill children who felt most stressed, she found, had the most extreme early aging of these cells. To unwind? "The first step is realizing you are stressed and noticing the signs ‑- you might feel your heart racing, or feel sweaty," Dr. Epel says. "The short-term way to reduce stress is to do deep breathing, what we call diaphragmatic breathing." The longer-term fix: "Make time in your life to do things that reduce stress."

2. Drinking too much alcohol ‑- or drinking too little
It's no accident that alcohol advice is following the bad news about stress. Putting your feet up and having a tall cold one is actually good for you. One or two drinks a day can lower the risk of dying from heart disease by a third or so, a study in the American Journal of Epidemiology found. Women are advised to limit intake to one a day, men to two. But don't imbibe more than that, or you'll up the risks of ill health, including strokes and cancers of the liver, throat and breast.

3. Moving too little
"Inactivity is an addiction that many of us have," says William J. Evans, PhD, a professor of geriatric medicine, nutrition and physiology at the University of Arkansas for Medical Sciences in Little Rock. But even a little bit of activity can extend our life, reduce the chances of being overweight, reduce stress and maybe even ward off Alzheimer's disease. "The first step is to just make the decision to be more active," Dr. Evans says. "That can be as simple as parking a little further away and walking or taking the stairs instead of the elevator." Then work your way up to the exercise level recommended by the Centers for Disease Control and Prevention: moderate-intensity activity such as walking for 30 minutes or more, five or more days a week.

4. Eating too much saturated fat
Saturated fats ‑- in meats, poultry, milk and butter ‑- can boost "bad" and total cholesterol and send you down the path of heart disease. Go Mediterranean, and train your palate to prefer monounsaturated fats found in canola, olive and peanut oil and polyunsaturated fats found in safflower, corn and flaxseed oil. "There's growing evidence that a more Mediterranean-style diet is healthy, even if you don't lose weight," Dr. Evans says. One smart goal, according to the American Dietetic Association: Keep saturated fat intake to 10 percent or less of your total calories.

5. Smoking cigarettes

More than one-fifth of U.S. adults, or 46 million people, still smoke, according to the Centers for Disease Control and Prevention. To reduce your risk of cancer and early wrinkling, grab some over-the-counter nicotine gum. In a review of 123 studies published in 2004, nicotine gum and other replacement treatments such as the patch upped the odds of quitting by two times compared to relying on willpower alone.

6. Breathing polluted air
Outdoor air pollution can cause coughing and burning eyes and is linked to asthma attacks and respiratory disease. While it is easier said than done, stay indoors as much as possible when pollution levels are high.

7. Getting too much sun
Every year, more than a million people in the U.S. find out they have skin cancer ‑- and another 55,000 find out they have the most deadly form, melanoma. Limiting sun exposure and wearing a sunscreen with an SPF of at least 15 cut the risk of skin cancer as well as wrinkles.