That is true of more than just a health class. We are making an investment each day in our future and not just in a financial sense. What we commit ourselves to today will determine where we end up. If we are wise with our finances we have the ability to be generous when God presents the opportunity. When we will engage and talk with our children even though we are tired at the end of the day, we are building a bridge for a deeper and meaningful relationship when they are older. If we will take the time to make sure that our spouse knows we love them today in a simple way it builds a foundation for a relationship that will endure tough times. When we make the commitment to healthy eating and exercise it creates a lifelong discipline that avoids the start & stop exercise regimen that most of us find ourselves in. If we are willing to step away from the computer or television so that we can intentionally engage in prayer and Scripture we develop a reliance on God that will strengthen our commitment to Him in good times and in bad.
Even as adults we need to see that what we do now is making an investment in our future. Our vision for that needs to be lived out in the decisions we make today.
Galatians 6:7 "Do not be deceived: God cannot be mocked. People reap what they sow."