Try to focus on one thing at a time so that your mind isn't all over the place. It's much easier to be disciplined when you're only working on one important thing.
Being disciplined isn't just about saying no to everything. It's okay to celebrate along the way. I'll even say that celebrating small wins is essential to developing self-discipline for the long run.
How can you make your goals easy? 1. Know yourself. 2. Work within your limits. 3. Focus on progress over perfection.
How can you hold yourself accountable? 1. Hire a coach so that you're financially committed. 2. Find co-workers/friends on a similar path. 3. Make your goals public.
Willpower is the last thing that you should rely on. You won't always feel motivated. You won't always feel like doing the right thing. The trick is to change your environment, hold yourself accountable, and set small goals.