So here's what I have to say. Unless you're Kate Middleton, repeating an outfit is OK. I suggest you repeat the entire outfit (if you must) only once. I personally, don't repeat the exact same outfit from head to toe, I usually play around with separates or wear different shoes for that matter.
A lot of women I know wear a dress for an event and then never wear it again, but then again,they do have the money for "a new dress every day". What I would suggest is, Don't repeat the exact outfit. For eg, If you've read THIS post of mine, You'll realize what I'm wearing in these pictures are very similar, But I've played differently with jeans and a tank top and I've also changed my shoes.
Now if you want to repeat a dress, try pairing it with a blazer or do something different with your hair and makeup from the last time you wore it.
The key here is to mix things up. Don't be afraid to play match among smart separates in your closet. Lay them out on the floor before you wear them and you'll get so many ideas, you wouldn't want to repeat an outfit!