31 Days to Waking Up Happy for Life

22. Don't Take Your Drink Lite

Aspartame, the artificial sweetener, may kill "friendly" gut flora associated with better moods. It also blocks the mood-moderating chemical serotonin (although effects were not noticed in people who had not had a history of a mood disorder). Together, these findings might help explain the results of a National Institutes of Health study: People who drank four or more cups daily of diet soda/diet iced tea had a 30 percent increased risk of depression compared to nondrinkers (more aspartame, higher risk).

23. Get Down and Give Me 20

You'll likely find that your fitter self is more resilient to slights, pressures and disappointments. Aerobic exercise increases the "fight-or-flight threshold," says John Ratey, MD, in his exercise science book, Spark—by relaxing muscles, boosting mood-moderating neurotransmitters (like serotonin and dopamine) and reducing the body's stress response to the hormone cortisol.

24. During Rush Hour: Pop One of These

What helps a frustrated, worn-out driver (besides vanishing traffic, of course)? Researchers at Wheeling Jesuit University in West Virginia found that pumping peppermint-scented air into the cars of ticked-off commuters helped decrease anxiety and fatigue. Stash a bag of peppermint candies in your glove compartment to help you keep your cool during a hectic commute.

25. Give Your Mind a Short Leash

"A wandering mind is an unhappy mind," wrote Harvard University psychologists Matthew Killingsworth and Daniel Gilbert in their study on mental presence. They found that people are happiest when their minds are in the present moment (yet another reason to meditate)—but that our minds are only in that state about half of each day. The three times we're most likely to be "here" and happy: when exercising, in conversation and (especially) when having sex.

26. Buy Mom Some Cashmere Socks

Researchers at the Harvard Business School, the University of British Columbia and the University of Liège found that purchasing anything for someone else—as long as it's within the very affordable price range of $5 to $20—makes you happier than buying the same item for yourself.