Simplicity, comfort, and details.
Simplicity in the sense that you should let your pieces speak for themselves. This is where understanding balance and style is of utmost importance. Let your clothes make the statement. Comfort in that you need to not only feel comfortable in the clothes but be comfortable wearing them. Your clothes are a fragment of who you are and who you want to portray. Stay comfy and you. Details in that everything comes down to the tiniest of details. Like an author writing a novel, every word counts and every word means something. Some may not see if, but it's there.
My style changes depending on my mood. I've come to a conclusion that when I'm lazy, the best thing to do is throw on something oversized with sneakers and call it a day.