Most medical and media discussion of mindfulness and meditation these days is about adults. People in their 30s, 40s, and 50s. These countless articles and studies shine a light on how to reduce stress from your job, your marriage, your kids, your health, and so on. That is all great, and all very important.
But what needs to be talked about more is how mindfulness and meditation help you make better decisions, rather than simply deal with the stress of decisions you've already made. Being quiet and mindful and honest with your feelings is a skill, not a tool you can just pick up and put down. The more you develop that skill, the more often and more efficiently you can utilize it.
So why start later? Don't tell yourself "I'm young and free, I don't have stress right now. I'll meditate later."
That's not the right way to think about mental health and stress. It's like they say about water in the desert: If you feel thirsty, it's already too late to drink.
Meditation helps develop your relationship with the true you. You may be unsure about this inner you, or embarrassed by it, or worried by what you might find. That's okay. Not all meditation has to be active, like the Taoists do. Over the years, I have found that sitting in a place of "thoughts of no thoughts," or Buddhist, Zen meditation, is just as important. Just sitting and experiencing the universe and my inner spirit are healing and grounding.
Don't wait until after you've made your major life decisions in your late teens and early 20s to start paying attention to how you really feel, and what connections to the world you really need. Let the times of quiet contemplation guide your life, not just react to it. It's like stretching and strength training and cardio: they prevent future physical illness. Practicing meditation and mindfulness when you are young are key to preventing future stress.