To start with, physical activity can help improve your sleep. And better sleep means better stress management. Doctors don’t yet know exactly why, but people who exercise more tend to get better deep “slow wave” sleep that helps renew the brain and body. Just take care not to exercise too close to bedtime, which disrupts sleep for some people.
Exercise also seems to help mood. Part of the reason may be that it stimulates your body to release a number of hormones like endorphins and endocannabinoids that help block pain, improve sleep, and sedate you. Some of them (endocannabinoids) may be responsible for the euphoric feeling, or “runner’s high,” that some people report after long runs.