Some people call depression a black dog.
This is a great short animated film about what depression feels like, with a good ending. Worth watching!
http://www.upworthy.com/what-is-depression-let-this-animation-with-a-dog-shed-light-on-it
If you are suffering from depression, counselling can help. I use CBT and other techniques with my clients who are suffering from depression. Don't ignore this serious health problem. Depression is a serious matter, and good counselling CAN help.