Working out stresses the body by destroying muscle fibers, taxing the cardiovascular system, and pushing the limits of lung capacity.
Working out also releases hormones, gets toxins flowing up and out, increases blood flow, moves the lymph, and can calm an anxious mind.
Exercising tears down for the purpose of building back up, so working out isn’t the whole story when it comes to to increasing strength or endurance. That is largely accomplished with eating healthily to repair the damage that the stress of exercise has caused, hydrating adequately, and getting good sleep.
Remember that if you have worked out really hard, eating well is a big factor in reducing the stress your body is dealing with (aka inflammation). What won’t help your body feel less stressed is consuming alcohol and processed foods.
Learning to listen to your body is so helpful. Sometimes it might need a hard workout for energy release and sometimes it needs to sleep or rest, to keep further inflammation at bay.