If you want to design stuff, you need to know some things. You should not be focusing on the software as much as you should be on art. That means you need to learn, but is learning all that you need as a designer? Certainly not.
The Ability to Learn and Improve
This may come down as quite the surprise, but being a designer requires you to look at other great pieces of art, including other designs, in whichever domain of design you want to work, and use them as a way of improvement.
Studying your competition is always great, as you know what they used to succeed, and more importantly, what is relevant as a design in that time period. Design favorites change, and like them, you should be able to change. Paying attention both to how you handle design and how the industry is changing should give you perspective on what is popular and what is not.
Learning to use programs is necessary as you will not be working on paper or canvas, most likely. You will be presenting your work through uncompressed images or videos, most of the time.
Working in a world where there is a lot of competition, many other designers, you should know how to wait. Opportunities arise, but people are quick to claim them. You should learn patience, as finding a client might take time. Even when you find a client, they might not know what they want, leaving you with redoing their design many times. Working with clients directly is not for the faint of heart, and patience is invaluable for this kind of work.
Some might say that creativity is not a skill, but it can definitely be practiced. Learning from other artists and designers and observing their work will inspire you and give you ideas. Using your own creativity, you can create something new, something which the client needed all along, but they did not know how to express it with words. Likewise, creativity can help you overcome walls and obstacles which will undoubtedly be in your way. It is almost impossible to be an artist and not be creative. Learning and practicing is an important way of honing creativity.
Knowing the limits of your own capabilities and that of the target audience or medium for transferring your design, like tablets, for example, should give you a better understanding of what the final version of your design should look like.
Hone your skills and practice a variety of approaches to design to stay at the top. Learn, improve, be creative and know where you need to stop your hand from drawing or painting more.