How to be more disciplined

Determine Accountability
Sharing your goals with someone you respect directly correlates to a higher likelihood of success. Some people may share this with a mentor, but telling a friend you respect or admire will suffice.
It can be as simple as informing your friend that you have decided to work on your overall self-discipline, or you can share some of your goals with them. Sharing about your journey will help you commit to it more strongly, as well as increase your chances of success.

Get Rid of Distractions
Because you can't be distracted by something that isn't there, the best way to deal with distractions before attempting to be more disciplined is to eliminate them. Put the remote in a different room if you take a break from working or studying to watch television.
If you have a habit of dropping what you're doing to check your phone, assign it to a family member for a few hours at a time. If you want to stop eating junk food, don't keep it in your house. This step positions you to succeed rather than fail.

Begin Small
Don't start your day with the self-discipline by attempting to accomplish something monumental. It will take far too long to keep you on track and motivated. Instead, set daily, weekly, and monthly objectives. Recognize every day when you accomplish your goals and know that you are on the right track.

Practice, Practice, Practice
Only by not giving up can you win! Self-discipline can take some people their entire lives to master, so don't give up if it's difficult at first. Continue to work hard, and if your goals all seem too big, make some very small ones so you can feel successful.