Having a goal around your actions is somewhat implied here.
So what can help us cultivate discipline? Well, each time you practice discipline you are cultivating it. So what can help us practice it?
1. Mindfulness; whether through meditation or other practices, practicing mindfulness can help you gain some distance from your thoughts and feelings and make a more reasoned choice to act towards your goals.
2. Environment; setting things up to make taking action easier (e.g. putting you shoes by your bed if you want to go running), or making things harder to do (throwing out all your junk food, not shopping when hungry)
3. Having compassion for yourself. You will never achieve perfect discipline. Realizing that you will screw up, especially in the beginning, and having compassion for yourself when you do (as you might have towards a friend who is struggling) makes it more likely that you will continue to cultivate discipline.
There is a good podcast that covers a lot of this that I think is well worth a listen. Don't let the title of it dissuade you; it is much more than just about depression and procrastination:http://www.myownworstenemy.org/podcast/why-procrastination-m...
Example: I've been going to the gym for a few years now. I don't have the best consistency for going, since I normally go after work hours. I found that by the time I was done with work I was tired and feeling burnt out from the day, and it was easy to skip going. I started making myself go first thing in the morning by waking up an hour early than normal and so far its working.
"Hey! Stop being a lazy piece of ...!"
When I tell myself that a task has world-class difficulty, and that accomplishing it would be an amazing feat, the task becomes highly daunting, and I procrastinate more. However, when I tell myself that the task should be done as a matter of course but that I'm being too stupidly lazy to accomplish it, the task becomes less daunting, and I procrastinate less. Expectations of normalcy change.
A similar effect occurs when you join a world class team and suddenly learn that they're doing ten tasks in a day that you once considered remarkable to finish in a week. Expectations of normalcy change, and big tasks seem far less daunting, so you procrastinate less.
gcheong's comment about environment is also spot on. Make it easier for yourself to stay disciplined. Reduce the amount of willpower/effort that it will take to start a task.
https://www.youtube.com/watch?v=_tE8kE8IfiY
https://www.reddit.com/r/getdisciplined/comments/5tln7k/meth...
That's what got me in the habit of budgeting/expense tracking and quitting caffeine.