What is the safety valve that prevents normal nondegenerate stars from self-destructing?

The safety valve that prevents normal nondegenerate stars from self-destructing is the outward radiation pressure that balances the inward gravitational force acting on them.

Stars shine because they fuse light elements into heavier ones, releasing enormous amounts of energy in the process. This energy is emitted as radiation, which exerts a pressure known as radiation pressure.

In a stable star, the radiation pressure from the star's core counteracts the gravitational pull of the star's mass, creating a state of hydrostatic equilibrium. This balance prevents the star from collapsing under its own gravity and ensures its stability over long periods of time.

In other words, the outward push from the radiation pressure acts as a safety valve, preventing the star from self-destructing under the influence of its gravitational force.