All of us from time to time feel down. It is perfectly natural to have these moments, the car breaks down, it rains on vacation, you lose a job. To varying degrees these events can and will make us feel miserable some times.
However, there is a darker emotion that can form like thunder clouds over a mountain, and these can be triggered without warning and seemingly no reason. They creep in and take the light away, the very joy of living disappears and all seems hopless in what feels like a never ending storm at sea.
This is depression, and it can drag a person down to a point where nothing ever matters. It is an illness and often a chemical inbalance and it can't be cured by simply telling someone to pull themselves together. There are varying degrees of depression and not everyone feels the despair of someone else, but the potential is always there for it to spiral out of control. People who are suffering need love and support, and any form of bullying will never work ,and you also have to remember that the sufferer has no idea why they feel the way they do.
It would pay us all to understand depression as it can happen at anytime to anyone.