There is no "right" way to seize your youth, as everyone's path is different. You are as young as you'll ever be in this very moment, so whatever age you are, don't just seize the day, seize your youth.
What I really want you to know is what you already know: when your insides are chugging along efficiently and things are working in harmony and balance you feel better. And when you feel better on the inside, your outside shines even brighter.
I won't pretend to sit here and know exactly how you should go about seizing the day and loving your sparkling, precious life. Only you know what thrills and depresses you, and so much of this comes from tapping the seriously-wise voice inside.