Give thought to what level of dress the day dictates. Think about the type of industry you are in and the type of people you interact with to determine the level of attire appropriate for your day: power professional, professional or business casual.
Benefit: Eliminates "wish I wore something else" feeling.  

Build your professional wardrobe to seventy percent of your closet.  These are clothes you only wear to work.  We spend the majority of our day at work.  So the majority of your closet should be composed of professional attire.
Benefit: You will always look professional.  Your clothes will last longer and you will save money.

Keep your business casual clothes a separate wardrobe from your weekend clothes.  On the weekend we are having fun and not paying attention to keeping our clothes clean.  They get washed more and fade in color quicker.
Benefit: You will save money, look and feel professional when on the job.