When, as a child, you are asked, "what do you want to be when you grow up?" You pick an occupation out of the air and tell the person who asks with little or no hesitation. Your assumption is that you can be anything you want to be. At the age of say 4 or 5 knowing this is nothing but fun, "I can and will be anything I want to be."
It's not until you get a little older that this is becomes pretty scary. If you once knew yourself and what you were made for, you have certainly lost that knowledge in the midst of the storms of life. You condescend to your old self, "I was naive, I didn't take into account the full picture of what being _______ would actually involve, I didn't really know myself..." You realise that perhaps you can do anything, but you no longer have that all encompassing parental provider to assert confidence upon you. You've discovered their fallibility, their finiteness, and you can no longer look to them as the source of all confidence.
While anything is possible, we only have a limited time. We are not blessed with the infinities of time to discover ourselves in a myriad of situations. It is into this poverty that the young and idealistic often lose the energy that propels them into an existence that affects those around them. They plug in to the system, at first to 'make-ends-meet,' but before long they are trapped by the fears of being uncomfortable, of not having 'enough.' That which once helped them live has become their only definition of life.
I don't believe for a minute that we have to settle into this slump, find our lives defined by our 'favourite programs,' or what phone we have, but I am now far closer to seeing how this happens.