I've been saying this for years. I don't believe in discipline. People who keep up a habit for years on end are not disciplined, they simply found something that works for them. If you try to start running every day after a couple of weeks you fucking hate it, then you need to change something. You might even need to stop running and try something else. Because it won't get any easier, and any excuse you have to break that habit you'll take eventually. Find things you will do without discipline. That's the secret.