I suffer from PTSD from a robbery that occurred a few years ago. Needless to say I don't enjoy being startled. (among other things, but I won't ramble) I just started a new job a few weeks ago, and one of the employees came by my office and scared the crap out of me by slamming down a piece of wood on the counter while I was engrossed in a task. So I am now freaking out, very shaky, and trying not to cry.

Any calming techniques since I can't exactly leave and go hide under my covers?

Any ideas on how to get this guy to stop (apparently he is quite the jokester) without coming off as a jerk and without going into detail about my issues?

Thanks so much.