A year ago I hadn't run a marathon, now I've finished three. Here are the business secrets I learned along the way:
Make your goal big and exciting.
Make a plan that starts very easy.
Very slowly increase the difficulty.
Sometimes you have to trick yourself to succeed. i.e. Run around a lake so you can't take a shortcut in the middle, run to and from work so you have a fixed deadline, pair running with other fun activities like your favorite podcast.