How can I...
 

How can I delete my post if for example I post something and I change my mind so I don't want that thing to be posted and I have no other idea what to post with editing?

You can write in "Delete this post.". You should do that with every post you make other than the ones in Hobo's thread.:D Or I think you can edit you post so it doesn't say anything at all.

Nah I can't edit by sayng nothing. It says that the message is too short.

First thing to do: Before you hit the Post button, invest a few seconds in thinking carefully about whether you really want to post that. I do this often, and I’ve frequently avoided posting something because of it.

Second thing to do: If the worst comes to the worst, do as Oddey says. We will very happily delete any of your posts.

No problem Max. ;)