How many genuinely repent of their sin and turn to the Lord, only to little by little enter a life of sin once again. When Jesus called the disciples He told them to leave what they were doing and to follow Him without looking back. It is our human nature to find an excuse to not do something , including following the Lord. Jesus said to continue to look back means we would not be fit for the kingdom.
The Cost of Following Jesus
And it came to pass, that, as they went in the way, a certain man said unto him, Lord, I will follow thee whithersoever thou goest. And Jesus said unto him, Foxes have holes, and birds of the air have nests; but the Son of man hath not where to lay his head. And he said unto another, Follow me. But he said, Lord, suffer me first to go and bury my father. Jesus said unto him, Let the dead bury their dead: but go thou and preach the kingdom of God. And another also said, Lord, I will follow thee; but let me first go bid them farewell, which are at home at my house. And Jesus said unto him, No man, having put his hand to the plough, and looking back, is fit for the kingdom of God. (Luke 9:57-62).
Returning to our sin is a sure sign we are not truly sorry for the wrong life we once lived, and by returning to the old ways once again only makes it worse for us as we see in the following passages (2 Peter 2:20-22) For if after they have escaped the pollutions of the world through the knowledge of the Lord and Saviour Jesus Christ, they are again entangled therein, and overcome, the latter end is worse with them than the beginning. For it had been better for them not to have known the way of righteousness, than, after they have known it, to turn from the holy commandment delivered unto them. But it is happened unto them according to the true proverb, The dog is turned to his own vomit again; and the sow that was washed to her wallowing in the mire.
As in the parable of the seed and the sower we see when persecution begins in the life of a believer they become discouraged and fall away from following the truth. When we repent our life is not immediately rainbows and sunshine. In fact it is the complete opposite, for our strength is no longer our own, but by Christ and the power of His spirit we are more than conquerers through Him who loves us! (1 peter 4:1-6) Forasmuch then as Christ hath suffered for us in the flesh, arm yourselves likewise with the same mind: for he that hath suffered in the flesh hath ceased from sin; That he no longer should live the rest of his time in the flesh to the lusts of men, but to the will of God. For the time past of our life may suffice us to have wrought the will of the Gentiles, when we walked in lasciviousness, lusts, excess of wine, revellings, banquetings, and abominable idolatries: Wherein they think it strange that ye run not with them to the same excess of riot, speaking evil of you: Who shall give account to him that is ready to judge the quick and the dead. For for this cause was the gospel preached also to them that are dead, that they might be judged according to men in the flesh, but live according to God in the spirit.