Disciple and Discipline are related! Without one you cannot have the other. A disciple of Jesus is someone who follows Jesus. If we are going to go where Jesus leads us, then we cannot be taking side trips. Therefore, a disciple needs discipline.

There is no exercising our calling without discipline. There is no bearing fruit without discipline.

Consider what the Bible says about the undisciplined life:

Through sloth the roof sinks in, and through indolence the house leaks. (Ecclesiastes 10:18)

The hand of the diligent will rule, while the lazy will be put to forced labor. (Proverbs 12:24)

The lazy person does not plow in season; harvest comes, and there is nothing to be found. (Proverbs 20:4)

I passed by the field of one who was lazy, by the vineyard of a stupid person; 31 and see, it was all overgrown with thorns; the ground was covered with nettles, and its stone wall was broken down. 32 Then I saw and considered it; I looked and received instruction. 33 A little sleep, a little slumber, a little folding of the hands to rest, 34 and poverty will come upon you like a robber, and want, like an armed warrior. (Proverbs 24:30-34)

In the Bible undisciplined and slothful ways are viewed as sinful.

Do you want to grow strong in Christ? Do you want to exercise your calling as a child of God with diligence and endurance? Do you want to flourish and bear fruit? Then take the advice of Psalm 1:

Delight in the word of God Meditate on God's word day and night You will be like a tree planted by streams of water! You will yield fruit when it is time!

Happy are those who do not follow the advice of the wicked, or take the path that sinners tread, or sit in the seat of scoffers; 2 but their delight is in the law of the LORD, and on his law they meditate day and night. 3 They are like trees planted by streams of water, which yield their fruit in its season, and their leaves do not wither. In all that they do, they prosper. 4 The wicked are not so, but are like chaff that the wind drives away. 5 Therefore the wicked will not stand in the judgment, nor sinners in the congregation of the righteous; 6 for the LORD watches over the way of the righteous, but the way of the wicked will perish.

If you are meditating on God's word day and night, you are learning to take your advice and direction from the Lord. You are giving care to walking in the way the Lord has for you. You do not follow the advice and ways of the wicked. Your concentration and the discipline of your life is to know and do God's will.