I have been driving my husband's truck this weekend since he has been out of town (he is coming back tonight, squeal!!!). If you have never driven a truck, I suggest you try it. At first, it was cumbersome, like driving a boat around town. I had to get used to its size and power. But now, after a week, I have found that the vantage point is fantastic. I can see everything going on, and I am bolder in my movements because I can trust the truck to accelerate quickly and I know that other drivers will let me pass because I am in a big vehicle.
It reminded me of the studies that suggest that taller people (especially taller men) are generally more dominant, more forceful, and command more respect due to their height.
One thing we talk about a lot in psychology (in fact, its the entire theoretical basis of many theories) is that viewpoints are SUBJECTIVE. This means that people that drive big trucks will percieve the world differently than people that drive flashy sportcars, or people who drive decade old Saturns that overheat if it climbs past 85 degrees outside.
So my recommendation, if you feel low or unassertive- get a truck. Drive it around. You will feel big and strong and find yourself a little more in control. At least, until you get back to the office.