It’s too obvious you say. We all know it. But do we really understand it? Spending your time on something is spending your life on it. You only have one here on earth.
The more you do something the more you become it. The first time you start running, you are not called a runner. If you run every second day and keep it up for a few months, people will call you a runner. Later you will receive other tags like “fit”, “in shape”, “healthy”, “full of life” and so on. It all starts with what you spend your time on.