Especially for younger undergrad:
Discipline is a skill, it can be practiced and improved upon incrementally. Try not to get discouraged if you have a bad day, or multiple days, where you would like or need to be. Don't quit. Don't spend the next week binging Netflix because you think it's a hopeless endeavor. Just get up the next day and try again. Each day try is more practice, you'll get a little better, and that continual improvement will pay dividends in the long run.
Keep at it.