what to write

I tend to never really know what to write on this thing. Well, I guess there are plenty of things I would like to write about, but I feel as though I probably shouldn't put them out there in the open. It's not that I am worried about people knowing certain things about me...but I am worried that I might offend someone. I also tend to want to write when I am mad/upset about something....so my posts tend to seem depressing....and I don't want people to think I am depressed all the time. So, how do you know when something is or is not appropriate to put on here? Maybe I just shouldn't worry about that anymore and I should just post openly? Hmm....