I've kept a journal since 2003, I was fourteen when I started. I talk about everything, personal life, politics, triumphs, failures. It's pouring your soul out on paper, or in my case, into a laptop.
Mine is intended to be read once I die. That way I can be brutally honest about everything because I'm not writing for anyone currently alive. Unless I die early.
This is a great post and journaling is a great habbit to start!