How can one stay positive and active?

Motion and action are life, I mean it's natural and goes by default while ceasing is a choice and unnatural, similarly staying positive is not an option alike negativity. Clouds are temporary during the day but the sun is permanent. The question is why and how you start feeling negative? Keep a track of what you take inside, here inside means what you hear or see or read and eat. Stay away from demotivated people, their opinions and experience will always be demoralizing, failure s and negativity will be a source of learning and result in growth. Darkness is only the absence of light and nothing else.