First i must ask you, what are your reasons or your MOTIVATION to stay fit? Is it for health? Is it to look more socially acceptable and appealing?
My secret is to find that proper motivation first, and then really amplify my motivation and focus on my goals so I would be able to work harder at the physical efforts I would put into fitness as well as the mental, which would be researching proper diets and workout plans.
Everything starts with proper motivation.