Get some fresh air this winter!! The furnace may be filtered but it blows dry, stagnant air and you know how dusty it gets in the house! Well you're breathing that dust too. Fresh air is invigorating! In through the nose and out through the mouth, get some deep breaths of crisp fresh air, take a walk through that snow..... what great functional exercise! Daylight on your face can really brighten your day, try to get that every day!