Make a positive attitude part of your daily routine. In the martial arts we are taught self-discipline. At first this self-discipline is in the form of holding stances and pushing yourself to do your best physically. With time and study the physical transcends into mental discipline.
In order to develop and maintain a positive attitude you have be aware of your thoughts and train your mind to go in the direction you want it to go. This doesn’t mean that all thoughts become rainbows and butterflies. It simply means that your mind & spirit are not pulled into the muddy waters of being negative. A negative attitude says this will never happen and a positive attitude says no matter what the outcome is I’ll do my best.
Remember that a Black Belt is not earned over night. It takes years of training, good and bad days, sweat, effort, and stick-to-itiveness to reach that level. So it is with your attitude. Put the time, energy, thought, and effort into your daily attitude and you will see the benefits in time.