Set goals. Regualry examine where you are in relation to those goals and if you aren't moving in the right direction, think about things you can do that will bring you closer.
Always have Plan B. Always know what Plan C might have to be if it comes to that.
Expect setbacks. Most successful people failed at least once, many failed so often it is hard to imagine they persisted. Raw stubbornness and refusal to give up are often a part of success.
Keep moving toward the goal. If you fall flat on your face, at least try to fall toward the goal. If there are mountains in your way, look for a path around them. Always, always, always be thinking of the goal.