Make a vow this fall to keep up that summer spirit by getting outside more often. To boost happiness take some time to explore the great outdoors. A recent study found that people hiking a mountain were happier and less fatigued than a group who walked hills on a treadmill, even though the mountain hike was more strenuous. Other research shows that a walk in the park versus a walk in a more urban setting, especially near a busy road, may soothe the mind and, in the process, improve mental health. Need more reason to spend more time in nature? Living near greenery may help you live longer, due to less air pollution, the opportunity for more physical activity and better mental health.