Feeling good about who you are and where you are in life will go a long way toward helping your body work at its peak. Sure, positive thinking alone can't help you lose 10 pounds or heal a paper cut, but it can go a long way toward helping you keep up with good eating habits and a physical-fitness regimen. You don't know what the future holds: don't assume it's full of bad things. Make your future is what you want it to be.