Starting a New Job - HELP!!

I have never thought of myself as an anxious person. Until now.

After years of cooking and bartending and managing in the food and beverage industry, my level of patience and stoicism were refined. Things have been thrown at me, my life has been threatened on several occasions, and relationships have ended, poorly, I may add. Through it all, I was constantly reminded of my AP Biology teacher, Mr. Kubiak, toting, "It builds character." When someone had to go the bathroom, "Hold it. It builds character." If a student wanted to take off his school-mandated sweater in May, "Sweat it out. It builds character." As much as I have come to agree with this, I'm starting to lose my mind!

I recently began a new job, hired as a copywriter, but with a much wider role than expected. I find myself waking up at 4 AM with an impending sense of doom. My heart races, I cannot get back to sleep, dread and despair creep into my mind. I can't help but think I may have made a mistake, I should have just stayed behind the bar where I belong!

Can anyone offer some advice on adjusting to an office workspace? On how to deal with fellow employees who grind your gears? On how to manage my newly developed anxiety?