"There are many rooms in my Father's house, and I am going to prepare a place for you. I would not tell you this if it were not so. And if I go and prepare a place for you, I will come again and receive you to Myself; that where I am, there you may be also. And where I go you know, and the way you know.” Thomas said to Him, “Lord, we do not know where You are going, and how can we know the way?” Jesus said to him, “I am the way, the truth, and the life. No one comes to the Father except through Me."
The gift of salvation is free to us because Jesus truly paid it all. But it costs us everything to keep it.
We have to learn to surrender all to Him, giving Him our all and all. If our hearts are not 100% His, the part that we keep as "ours" and not His, will take over the rest.; unconfessed or repeated sin, pride, bad habits, lust, whatever comes fist at taking God's place (any idols) will give the legal right to the devil to attack and rob us and will come between us and God. Paul is very firm when He is addressing to the Corinth Church.
1 Corinthians 5:6-8
”Your glorying is not good. Do you not know that a little leaven leavens the whole lump? Therefore purge out the old leaven, that you may be a new lump, since you truly are unleavened. For indeed Christ, our Passover, was sacrificed for us. Therefore let us keep the feast, not with old leaven, nor with the leaven of malice and wickedness, but with the unleavened bread of sincerity and truth.”
The quicker we repent after we sin against God, the faster we are forgiven and the enemy has less room to hurt us. We must realize that we are born again and our spiritual man (inner man) is completely new and transformed by Holy Spirit that came to dwell in us when we asked Jesus to be our Lord and Savior, the less we will fall into the temptations that the enemy brings on our path.
Let's take a look at what Paul said about himself : "But I discipline my body and bring it into subjection, lest, when I have preached to others, I myself should become disqualified." (1 Corinthians 9:27)
To renew our minds, to erase the old "worldly programming" from the life we lived before Jesus became our Lord and even much of what we learned growing up; we need to feed on His Word and spend time in God's presence on a daily basis.