My parents are well-defined people. They know exactly what their life looks like and what their position on anything is. They've filled in everything that defines them and are content with things staying that way. To them, being alive is about having a complete definition of yourself, but it does not necessarily include actively changing that definition. Sure, once in a while a blank might show up that they haven't defined yet (new political crisis opening up, new technology they need to learn), but as soon as they've defined it once, they won't bother changing it since they're too busy doing all the other stuff they've already defined themselves to do.
Young people are (of course) not well-defined. They're full of blanks, and because they have so many blanks, when a new area appears that they need to define themselves on, they often don't initially choose their right personal 'answer'. Because that would require experience. It also makes young people a lot more flexible on things, as they know that their judgment can be off and they're ready to redefine themselves in an area if needs be.
I'm in my late twenties now, and am perhaps in a dangerous time. I've surpassed the initial blank stages of life and have even realized that I'm quite pleased with a lot of the blanks I've filled in. There's some core concepts in my life that I have not, and have not had need to, challenge. But it's easy to generalize, and this way of thinking can lead to overconfidence in areas where it's not justified. I'm tempted to not challenge my initial definition of myself in some areas, knowing that I now have the ability to accurately define myself right from the get-go in some other areas. At the same time some of those steadfast definitions are being challenged, and I am illogically reluctant to let them go.
That's not to say that the ways of the elders are best. These actions of defining oneself upon an area are perfect examples of pattern recognition and pattern matching. If you've been trained with one specific set of patterns, you might have an extremely well-trained neural network for most everyday situations of, say, the 1980s, but when something like the internet comes along you simply have no way of defining it for yourself with your existing experience, because there is simply nothing like it. The only thing you can do at a moment like that is to let go of your old, perfectly-trained but situationally-limited, network, and start training a new one from scratch. I believe that as you get older, this gets more difficult for two reasons: 1. we're more reluctant to abandon our previously trained networks, and 2. even our 'from-scratch' network already has some built-in pre/misconceptions that we simply cannot undo.
How does one deal with this? Personally, I write blogposts about it, drag it to the surface and confront it every once in a while. Getting meta usually works on this stuff as it makes you realize what definitions of your own might need challenging. It's important to revisit your definitions every once in a while to see if they still hold. Everything changes, always. Continuous integration of the mind is a great way to do sanity checks on yourself to see if you still really believe in what you think you believe in.
Never take anything for granted. Always challenge your basic beliefs. Continuously redefine yourself.