You can cue Mr. Miyagi of Karate Kid fame if you must, but find the most mundane, time consuming task that you can muster (scrubbing the bathroom tile grout with a toothbrush, clearing a football field sized meadow with a scythe, whatever) lock away the phone, the tv, ALL distractions, and get to work. Whatever thoughts pop into your head, pay them as little mind as you would your crazy racist uncle. Don’t actively expel them, just let them pass and fade away naturally. Come back to focusing on your breath and the task at hand. Be in the moment. Forget about the goal. Forget about the rewards. Forget about your lengthy to do list. It will feel uncomfortable at first, but with enough practice, you’ll find contentment in the moment even doing the most seemingly drudging task. This will build your mental endurance substantially and get you to the finish line.