Every challenging exercise should be followed by a period of relaxation and observation of the stressed body part(s). This serves as training of bodily awareness as well as allowing the necessary time to transport fresh blood to the stretched and squeezed muscles in order to provide the necessary oxygen and nutrition.
As the transition from lying down to a sitting posture can put a lot of stress on the lower back, a few possibilities of how to do this in a gentle way are given below as well.