How can you tell when it's the right time to request an extra therapy session, and what should you expect from it?

How do I save myself? Im 21 F, my father is extremely abusive to me and my mother. It has been going on for the whole span of our lives. We are planning to move out but im scared he'd follow us and cause a problem there. What should I do?
Have you ever been invaded by a bug during a high-stakes situation? If so, what happened?
What are effective ways to cope with the annoyance of missed therapy sessions when rescheduling isn't possible?