There is a certain nonchalance and comfort level necessary in order for a man to look his best. You should act comfortable in your clothing, and not worry if your tie is not perfectly straight, or your shirt is not perfectly tucked. A confident man gets dressed once - before he leaves - and doesn't fret about constantly fixing his look.
Some men (and I can think of one of my friends in particular), especially when "dress up", constantly pull at their clothes and try to fix the natural imperfections of their look (shirt coming slightly untucked, tie flailing with movement, hair a little "messed up", etc). This makes a man look insecure and overly concerned with his appearance.
The "best dressed" men are usually those who are most confident. I love seeing a guy in a slim tailored suit running or doing something active...after all, those are just his clothes, they don't stop him from living his life. Wear a suit like you wear a t-shirt...don't worry about your clothes...they're just clothes...act natural.
This is one of the appeals of Ari Gold from Entourage - he is always well dressed, but above that, he is confident in his look - often running, rushing, and doing big arm gestures, etc. The imperfections add to his appeal.
If you looked good when you left the house, you still look good. If you must, you can check yourself out in the mirror when you go to the bathroom and make sure you are still in order...other than that, go out and act natural.
Yours in style, Style Blogger.