"Slytherins have a more cynical view on the world, and believe that there is darkness in the hearts of all, some are just unwilling to accept it. They think anyone who doesn’t realize this is naive or perhaps even stupid, and because of this they can easily clash with Gryffindors or laugh at Hufflepuffs. This said, Slytherins are absolutely in no way evil, some are actually very good.
They simply have a drive that carries their life, and if you get in their way you better watch out. Slytherins have an almost bloodthirsty craving for success, and if they don’t think they can achieve this then they can easily fall into a darker place of self-loathing and take this out on others. Love and accomplishment are the two things that mean the most to them, and they do not understand that the need for the latter can drive away the former, and when the feeling of pride fades or they fail at something, their possible lack of something dear and close to them can hit, and when it hits it hits hard.
Slytherins are very emotional, however unlike Gryffindors they very rarely show it. Instead they bottle it up, using it in other ways, some of which may be artistic.
Slytherins can very easily connect to art or music. Slytherins usually pick one subject they feel for and stick with it, rather than focusing on them all.
This can be an issue academically, and some Slytherins may even drop out of school, but despite this their ambition will drive them to doing something they love, or they will have a downward spiral into depression. Lawyers, doctors and artists are often Slytherins.”
- Slytherins: Hogwarts, A History; found and originally posted to Tumblr by bloodydeliberations.