_Rhythm_ is a way of trusting the future.
This sounds poetic, but is also quite literal!
To entrain is to assume: something will happen again; it will happen around about when expected; it is safe to commit energy in advance.
It is a minimal form of trust.
Despair is characterised, in part, by a breakdown of such trust. The future becomes either threatening or blank.
Rhythm gently reinstates futurity.
A pulse says: you can lean forward; time will catch you.