It really is true: the memory is the first thing to go (if it was ever there in the first place). Which is to say, at 29, 15 is almost half a lifetime ago, and I honestly don't remember enough about it to say anything useful. I can recall a couple of events from that year, but nothing really important, no major decisions of any kind. I could come up with advice for 19-year-old me, most years since then, maybe even 18-year-old me. But 15-year-old me isn't even important anymore.