Recovering my gym schedule against sub-health

Recently, I can feel that my body's condition is falling into a sub-health state. Since I feel tired all day long, while it is hard for me to have a good dream at night consistently. My thoughts are always in congestion and I can not concentrate my vigor on my study materials. By the way, more than half a year has been passed since the last time I do my gym exercises. I know I need a new start, I need to recover my health schedule. No matter how hard work I have to do, No matter how many exams I may take and how severe the study goal I will endure, protecting my health and keeping my youth are always my first principle!!!