For if ye shall diligently keep all these commandments which I command you, to do them, to love the LORD your God, to walk in all his ways, and to cleave unto him; Then will the LORD drive out all these nations from before you. - Deuteronomy 11:22-23

We wonder why the Lord does not drive out and subdue our besetting sins. We do not possess them, but they us. The explanation is to be found in our lack of consecration. We do not keep all His commandments, or walk in all His ways.
 
God cannot deliver us from besetting sin unless we yield ourselves to Him entirely. - It is only when He is Judge, Lawgiver, and King, that He can save us. The great surgeon will not undertake a case unless he have its entire management. The general cannot protect a town until it has passed over its government entirely into his hands. If you would give yourself utterly and unreservedly to God, you would find how strong He is for those whose heart is perfect toward Him.
 
Unless we obey all His commandments; - because they contain His precise direction as to what we should, or should not do. If you want your medical man to heal you, you must abstain from things he forbids, and do those he prescribes. You cannot expect God to save you unless you utterly and reverently obey all His commandments; that, for instance of not having fellowship with the world and its ways.
 
Unless we cleave unto Him. - There must be the daily walk with God, the abiding in Him, the holy and unbroken communion. "He that saith, I know Him, and keepeth not His commandments, is a liar, and the truth is not in him. But whoso keepeth His word, in him truly is the love of God perfected." "He that abideth in Him sinneth not." The anointing of the Holy Spirit will teach us this sacred habit (1Jo 2:27). But entire consecration must precede entire deliverance.