There are some people who have the ability to learn certain skills much easier than others, and at a much faster rate. Some people are taught certain skills during their childhood. For example, someone might have learned how to speak several languages because they grew up in a family where several languages were spoken. Other examples could be people who learn how to play an instrument as a child, or persons who are taught to drive at an early age.
Everyone has the ability and the capacity to learn, if they have a strong enough desire to do so, it just comes down to taking the time to develop the desired skill. As with anthing else, when you are learning something new, you start with the basics, and then you work your way up to the more complex elements. Once the basics are learned, then you have to practice, practice, practice. Remember no one learned to drive by simply reading books.
Learning a new skill always seems complicated in the beginning, and you are going to make your fair share of mistakes, because you will have to concentrate on many things at the same time, but gradually your newly learned skill will become second nature, and you will be able to perform it without thinking. Your skill level is based on your preference, you may choose to stay at an intermediate level, or you may choose to reach for the stars, as the sky is the limit.
These same ideas apply to learning the skill of how to be stylish. First you will need to learn about your body shape and your porportions, along with learning about colors, optical illusions, and much more. In the beginning, it will seem difficult to think about all of these things at one time, but the more you practice, the easier it will become. Soon the process will become as natural to you as brushing your teeth, or driving your car.