Success is not the destination but the road to your destination, like any road being traveled the engine may breakdown, the AC may stop working, and you may get stunned by driving over pothole and dents on the road but you are succeful because your persevere you keep it going and keep it moving. No matter how many dust clouds, thunderstorms, and fatigue, you have to keep it going.
Another way which is define success is also by someone's mindset . For example, a dishwasher in a restaurant although it may not be "the American dream" of success but in the eyes of family he is success because has providing stable income, or could be dishwashing to put himself through school, or simply building his resume before moving up and opening his own business. It's all about the mindset, with success as a mindset, failure is never an option, no matter how long it may take one to achieve their goals.
Success is also defined as the realization. Meaning the point in one's life where one may look back and realize that the sweat, tears, pain, and worry were worth it or better yet they were miniscule compared to how great the reward of accomplishing your goal is. Success is not the high paying job, but the self-fulfillment. Teachers for example get advance and expensive degrees only to work in a job that pays less