[solatic]

To answer without using the word "meaning":

Life satisfaction comes from devoting yourself to the pursuit of something that you feel is important. Because it's important, you can see and feel the effort that you're putting into it, therefore your effort is important, therefore you are important. Different people consider different things to be important.

Youth is about experiencing many different things so that you can figure out what is important to you. Growing up is making the decision to shut the door on everything that isn't important so that you can focus your time and effort on what is important.