I was speaking to a friend today and I was telling her one of the major reasons I wear a necktie to work. It's not a job requirement, but I told her that if I walk out the door in a tie then I've started by setting my standard high. I go to work casual and my work suffers.
When you dress nice you feel good. You're ready to take on the day. It affects your mood, and your actions. Anytime I meet an associate who's appearance is poor can be a direct reflection of their work. There are special situations, but my experience has shown it is.
Don't start your day lowering your standard. When I walk out the door in the power tie feeling and looking like a champ it puts me in the right frame of mind. You don't have to wear a tie or business suit, but if your clothes are wrinkled, don't match, or you hair is messy it says a lot about where your head is at. Make sure your day starts right. Set the standard for your day in the morning so you spend the day trying to meet that standard instead of giving up before coffee.