Fast energy release in the corona, whether powering coronal heating or solar flares, typically involves large numbers of turbulently forming and evolving reconnection regions. This complexity can be intimidating, however, important global properties - including the amount of energy released and the magnetic structure that survives - are often insensitive to the underlying "microscopic" evolution. We present a new step forward in magnetic relaxation theory, based on the evolution of field line helicity, that greatly improves prediction of the end state and the energy released. In particular, our new approach is shown to accurately predict the outcome of an MHD evolution of a braided magnetic field. The new theory also explains why turbulent energy release often produces a nonlinear force free field, even when turbulence is well established, which is a strong advantage over longer-standing relaxation ideas.