Searching around the computer this morning, I stumbled upon an amazing quote on http://dresswithstyle.com, from the infamous Hardy Amies Book, the "ABC of Men's Fashion", on page 108 we find:
"To attain style in dress, you must look perfectly happy and relaxed in your clothes which must appear part of you rather than a wardrobe you have just donned."
Splendid! I should even be so bold to say that this reminds me of my own personal mantra:
"Dress up your sportswear and dress down your formal wear."