Are you in a bad funk today? Treat yourself to a bar of dark chocolate. Or jump on a trampoline. Or get a nice plate of leafy greens at your neighborhood salad bar. Though a crabby mood is most often circumstantial—such as bad traffic, an unpleasant boss or simply sleep deprivation—you can try giving yourself a natural mood boost with vitamin B12 or simply straightening your posture and not slouching your shoulders.