Something that was missing from two of the three creative courses that I completed after high school, was how to make a living from your work. How do you draw up a contract or a business plan or an invoice? Virtually non of this was covered.
Probably to toughest aspect of design isn't creating something visually stimulating, most designers can do this naturally. However, listening to your clients needs and wants, and then producing a great design is key to offering a functional design and a usable product them to take away.