I'm not well equipped for adulthood.

You know, adulthood is not what I thought it would be. I thought that when I hit my mid thirties I would be this really together person who knew what to do in any situation. Where does that idea come from? Is it to do with people always telling you as a child to wait until you're an adult and then you will understand? I think it would be more honest to say wait until you're an adult and then you can let on like you understand.
Seriously, I thought that one day, when I worked my butt off (turns out that doesn't literally happen either) and got a great job running a company, I would just be so together and "with it." Apparently I put on a great show because everyone seems to think I've got it down pat. Friends are calling me asking advice about their job or their company. I say (with sage wisdom in my voice) whatever pops into my head. They thank me. We hang up. I spend the next five minutes wondering why the hell they would ask me ANYTHING, let alone business advice.
So, I wonder. Will my whole life be like this? Do elderly people still wonder when they are going to get it together? Am I the only one who feels this way?
It's ponderous I tell ya...