When it's cold outside, nothing feels quite as good in your belly as piping-hot soup. But the comfort factor doesn't stop there. Lean red meat is an excellent source of tryptophan and protein, both of which are critical to mood regulation. Dial down the unhealthiness quotient by trimming any excess fat before putting the meat in the Dutch oven or slow cooker. It's also a health-conscious move to prepare the dish with stewed tomatoes or a beef broth rather than fat-laden gravy. Toss in a few serotonin-enhancing potatoes and some vitamin-rich vegetables to create an all-around satisfying meal for your taste buds and body.