Our mind is the source of ALL emotions, good or bad. Whatever we feel it is always inside of us. We cannot feel good or bad outside of our mind. So this mind is responsible for our happiness, our sadness, and everything else in between. It is the NATURAL job of the mind. For most of us ordinary people, when the emotion is angry we say I am angry. We identify ourselves with the mind. Because of this our moods, our feelings, our emotions swing according to the works of the mind. One of the greatest discovery of the Buddha was that we don't need to follow this mind generated emotions when we get to understand what this mind is.