One of the best remedies I have found for this is a good session of self talk. Often, when we take the time to check in with ourselves and recognize what the problem actually is, we are better capable of turning ourselves around. We can take steps to combat the funk, whether that take the form of positive self-imaging, a run, or a hot bath.
When you settle in for an internal chat, make sure to keep your coaching voice positive. You should not be berating yourself or knocking yourself down for perceived failures. Instead, recognize your feelings but then recall all the reasons why you are so awesome. Because you are.
You are one bad-ass bitch.