"
and falling off
It's all over for you
For you!
When you're on
This could be a way of describing the way it feels to have mental illness, to be "on the edge" of sanity and having to balance the pain inside with the life outside. This certainly could speak for people who feel their life is over because they are mentally ill, especially those with Axis 2 diagnosis.
(Axis 2 Mental illnesses take years of medication and therapy but can be present throughout life ie Never Cured, examples of this include Schizophrenia and Borderline PD - opposite to Axis 1 disorders such as Depression and Anxiety, which while just as distressing, can be "cured" with medication and therapy.)