What does "slip away" mean here?
In this context, to “slip away” means to pass quickly (out of existence). It is often used to mean that one is losing lucidity or their consciousness, which is likely the meaning meant by the speaker here. Ex: After drinking too much, he could feel himself slipping away. Ex: It was all a blur; I felt myself slipping away. In other situations, to “slip away” can mean to leave secretly or quietly. Ex: He slipped away in the dark of the night. Ex: He slipped out of the prison cell quietly.