2 Corinthians 10:3-6 For though we walk in the flesh, we do not war according to the flesh. For the weapons of our warfare are not carnal but mighty in God for pulling down strongholds, casting down imaginations and every high thing that exalts itself against the knowledge of God, bringing every thought into captivity to the obedience of Christ, and being ready to punish all disobedience when your obedience is fulfilled.
The first king of Israel, King Saul,was told by God to utterly slay Amalek and his descendants. In blatant disobedience Saul allowed Agag, the king of the Amalekites and the best of the cattle to remain alive. The following day, Saul tried to remedy his disobedience by attempting to sacrifice the best of the cattle to the Lord.
But the prophet Samuel informed Saul that because of his disobedience, his family would no longer reign over Israel, and he told Saul, "to obey is better than sacrifice." If offering the "best of the cattle" for sacrifice was a poor excuse for disobedience, its negative consequences must have paled in comparison with sparing the Amalekite King - whose infamous descendant Haman, an agagite (Esther 3:1) later rose to power seeking to destroy the entire Jewish population of Persia.
If Saul had dealt with Agag as God instructed him, he would have spared his people, centuries later, from the agonizing contest with a vicious enemy who would destroy them. So it is with sin. Allow it to live and be sure it will return to slay you with more power. Don't compromise. "Small" sins lead to bigger ones, and soon enough the early footholds that are ignored will turn into strongholds which cannot be!
"Take no prisoners" when dealing with sin -- seek to be rid of the little sins, so that later you will avoid the strongholds that may threaten to compromise or destroy your walk, your calling, your life, and the precious relationship that the Lord has purchased for you!