There are too many 'growing up' posts in this blog already. But the thing is, I don't think you can ever really grow up completely. You 'grow up' in different ways at different times.
You accept that the world isn't perfect.
That no one is perfect. Nothing is perfect.
What is perfect is a mishmash of many separate things that don't come together.
People come and go. Some stay a little longer. Some are people you meet along your own journey - with each of your lives going different ways but crossing for an instant. But some become more than that - they become part of your journey, part of your life. They are friends. You need them. But you also need the other kind, for diversity. For moments. And being able to separate them is important too and its something that comes in one of the later phases of 'growing up'.