Constructive rest is one of the best relaxation techniques you can know. In constructive rest, we take the body into a completely neutral position where there can be a deep release of tension held in the body/mind system. When that happens, a kind of re-set can happen that takes us into a place of being centered, present, and available to the potential of the moment.
Consider what Liz Koch, an expert on the psoas muscle, says about constructive rest in my interview with her, Does the Psoas Speak Pilates?: "It's a being (not doing) position. Before you exercise or at the end of the day, constructive rest changes the whole expression of the central nervous system, of which the psoas is expressive. It is a messenger of the central nervous system - a bridge between upper and lower body, between the enteric brain and the gut brain, and expresses the messaging between sympathetic and parasympathetic. There's a lot going on in constructive rest, but you're not doing it. You just allow it to happen.