It's very common for teens to believe that somehow they have caused their parents to separate. You may be asking yourself things like, "Was it something I did?", or "Is it my fault?". Or thinking, "It wouldn't have happened if I hadn't argued so much, or I had done better at school, or..."
If you are saying things like this to yourself, stop! It's not your fault.
Remember: Parents separate because of problems in their relationship. You are not the reason why they are separating.