On many boards, deleting posts and threads by members and moderators can cause a database error.
Instead of deleting posts/threads, those unwanted posts can be moved into a moderator forum, so as to make them invisible to members.
Here is a thought: type your post in a PM to yourself, then in the morning after a good sleep, review it. You can always delete it or post it later after editing it to suit your tastes.
edited to add:
A technical question:
Does the act of deleting PMs also mess up the database?
Is there a preferred way to delete PMs, or do we even need to delete them here?