Adults (people who see things in a more adult way, not necessarily legal adults: two very different things) tend to see things through a more complete lens. The more adult one is, the more clear and complete is their picture of the things they perceive. They see more from the same picture. That’s really what wisdom is, but a sort of active wisdom that influences real decisions, not the kind you see old sages and philosophers preach about.
Its like the difference between a 22 year old choosing to get drunk in a bar on a Tuesday night versus a 42 year drinking responsibly at home on a Sunday with the neighbors.Real adults don’t need crazy stimulus, or materialist tokens, or have self destructive tendencies. They have a certain self contentment and stability because they see the truth in things, and know that their happiness, success and self fulfilment comes from within themselves.
Really then, being an adult is kind of like emulating Buddha. He perfectly understands himself; what makes him happy, what does not, what improves himself, what does not, who he is, who is not. He has a perfect sense of clarity about what to do, and what not to do in his life.
This is not to say that he knows everything, and has somehow mastered the universe; simply that he has mastered himself, and knows that is enough to lead a good life.