Actually no.  So the first thing that you have to do is take this idea out of your mind that you are somehow old or mature or middle-aged.  A lot of experts actually think that the forties are the new thirties (Related article:  Forties are the new thirties, particularly for women).  

Fashion tips

• Keep reviewing your style.  A woman needs to have her very own style but at the same time this style has to evolve.  While you may have looked very pretty in a certain outfit, that will not work for you now - your body has changed and the world has changed.
• Take a look at your wardrobe.  If you don't know where the Salvation Army office is in your town, just take your old clothes and throw them in the garbage.
• Unless you live in some remote place, there is much more acceptance for women in their 40s and older to be able to dress any way that they want.  This is something that was unheard of just 10 years ago.  So if you have the body and the attitude, mini-skirts or low-cut dresses are perfect for you, like Ali Larter.
• Stay up-to-date by reviewing many fashion websites and watching the television programs, particularly those that feature real makeover cases.  (For example, Queer Eye for the Straight Girl, The Swan, Extreme Makeover, etc.)
• Seek advice.  If you can afford to, get an image consultant (many are available for online consultation).  If not, watching programs like "What not to wear" will help you a lot.  You can always seek advice and input from younger friends and family members.
• Use the resources available.  For example, if plastic surgery is going to help you get the body and looks you want, it might be worth it.  If losing a few extra pounds will help you fit in certain types of clothes, take the challenge.
• Don't be afraid to try.  Take risk and you will notice the difference in your personality.

Recommended articles:  How to have a makeover after 40?     Fall fashion

Style to look younger     Style makeover when you cross 60     Dating in 40s