The first thing you have to have to be a successful designer is passion. Design is not easy. You will never be satisfied with what you create. You will always have someone, whether online in a comments section or someone you work with, doubting your creation. It is your passion to create, to solve and execute your ideas that will get you through the highs and lows of your budding career. It is what made you want the career in the first place so never let it take second place to anything else in your life. Because once you lose the passion you will lose your drive.