People can be sad for many reasons. Some may be genetics, like chemical brain imbalances. I get these awful feelings too and just don't want to get out of bed. What helps me the most is to just do things. It can be as simple as cleaning up your desk. Learn something new. Just do something. That takes my mind off feeling sad and I often get a lot of enjoyment from the task I completed that lasts for a while and makes me happy again. However, the sadness often creeps back in, so I start new projects. It is a constant struggle for me.