A few weeks ago I, along with others, was asked to recommend books for a teenager. We were asked specifically to avoid any that were classified at Young Adult. When queried as to why this was, the requester stated that the teenager had outgrown YA and wanted something less aimed at children. This upset me greatly. I, alas, am no longer able to classify myself as youth, but some of my favourite books are YA. And am not the only one: http://www.theguardian.com/books/2015/mar/20/young-adult-books-that-grownups-should-read or http://www.huffingtonpost.com/2014/06/06/young-adult-books_n_5460818.html .
But what does this have to do with writing? Well, everything. And it can go two ways:
One: act your age – write about what it’s like to be a thirty-some parent or a fifty-odd divorcee or an OAP on a quest for love. There are so many stories related to your life as it is right now. Write them.
Two: don’t – write about what you yourself were like, would have been like, could be like in the future.
That’s enough to get you started. And if you’re stuck, you can start writing about someone else your age, or not. Whatever you do, don’t let publishers’ categories put you off.