I will consider the case of a CFT deformed by a relevant perturbation resulting in a mass gap. I will argue that in such a case, operators of high scaling-dimension can decouple exponentially quickly from low-energy bound states. This observation motivates a new way of solving strongly coupled theories using a conformal basis on the light-cone. In particular, I will describe the method applied to 2D QCD-like theories both at large and at small N. I will also describe progress in formulating the approach in 3D.