John 8:31
31 Then said Jesus to those Jews which believed on him, If ye continue in my word, then are ye my disciples indeed;
Luke 9:62
62 And Jesus said unto him, No man, having put his hand to the plough, and looking back, is fit for the kingdom of God.
-A disciple by definition is a follower of a particular discipline. The word “disciple” is right there in the root of the word “discipline”. It takes discipline to keep your hand on the plow and not look back (Luke 9:62); just like it takes discipline to read your Bible every day (Psalm 1:2), pray every day (1 Thessalonians 5:17), be a light and a witness every day (Matthew 5:16, Acts 1:8), etc. It’s a lot to expect, but the Lord doesn’t expect it from everyone, He expects it from His disciples. How can any of us call ourselves disciples if we lack the discipline to follow Jesus?