Taking a moment to stretch is a great way to alleviate stress and improve your posture, mobility, and muscular tightness (especially in the back). Spinal health is wealth.
In addition to calming your mind, deep breathing can also lower your blood pressure and other physiological responses to stress. It may also aid with concentration.
Without leaving your house, a wall sit may provide your legs, glutes, and core a rapid jolt of energy.
Planking can help you find strength in stillness (and your core).
The feel-good hormone oxytocin is released when people help one another and show appreciation.