When we accept God as our Saviour, we enter into an intimate relationship with him. The Bible compares the love of a man and woman to the love God feels for us. It compares a marriage with how the Church (us) is married to God.
Ephesians 5:25 ESV /Husbands, love your wives, as Christ loved the church and gave himself up for her,
Ephesians 5:22-33 ESV / Wives, submit to your own husbands, as to the Lord. For the husband is the head of the wife even as Christ is the head of the church, his body, and is himself its Savior. Now as the church submits to Christ, so also wives should submit in everything to their husbands. Husbands, love your wives, as Christ loved the church and gave himself up for her, that he might sanctify her, having cleansed her by the washing of water with the word...
So therefore, when we let Satan tempt us and we sin, we are dealing with him instead of God. In essence, we are cheating on our relationship with God.
A small sin might be equivalent to lusting after another while a bigger sin might be equivalent to fully being intimate with another person.
Our relationship with God is important and special and we are to be faithful to God.
Deuteronomy 28: 1-2 / And if you faithfully obey the voice of the Lord your God, being careful to do all his commandments that I command you today, the Lord your God will set you high above all the nations of the earth. And all these blessings shall come upon you and overtake you, if you obey the voice of the Lord your God.This does not mean that if we sin, God will "break up with us." He is faithful to us as well and will not abandon us because of a little sin. As long as you repent of your sins and try to live a sinless life he will always be there for us.
1 John 1:9 ESV / If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness.
The next time you are tempted to sin, remember that you would be cheating on God and stay faithful to him.
James 4:7-8 / Submit yourselves, then, to God. Resist the devil, and he will flee from you. Come near to God and he will come near to you.