Everyone experiences sadness at some point in their lives. It is usually due to disappointment, frustration, or the loss of someone dear to us. Sadness is natural. Time heals, the mood improves, and people go about their lives. However, for some people, depression can be so severe that it takes over their lives and prevents them from managing it. Depression of this severity is a medical condition that requires proper treatment. Again, feeling sad is normal, but when it become