Life is but many moments on after another. Not one moment stays. One moment is arriving every moment and other moment is leaving every moment. If you live in moment past you become sad and depressed. If you live in moment future then you are anxious. Both are waste of energy and depletes your energy and make you sick. So live in moment present, no past or no future. Just in the moment. Totally present right now. I know it's easily said than done but by practice slowly slowly we all can achieve this.