There's no idea that can't be explained to a thoughtful 14-year-old. If the thoughtful 14-year-old doesn't get it, it is your fault, not the 14-year-old's.
Every future turns into the past. The richness of your past dictates what you are today. It's not your decision what you are today, but what you will be tomorrow. This is where a part of your decision comes into play.