How can I change my life around? It's like everything is falling apart for me. I pray repeatedly, but I find myself doing the same sin over again - drinking, smoking cigarettes, looking at porn, lusting, cheating and everything else that's worldly. I don't want to do any of these things anymore. I just want it to be over. I am in church every Sunday with my wife and kids. When I step foot in church I want to give God 100% not 50% of me, but I know I am going to be doing the same thing when I leave. It's like I can't do anything right with my life or my marriage. I am sick of living a lie. I just want to find God and never look back on my sin. I wish this curse on no one.
It appears that you are expecting an outside force, like God, to change you without your involvement. You take the paths of least resistance and then are surprised that they don't lead to God.
Repentance is making up your mind that you no longer what sin as a part of your life. It is more than just being sorry about having sinned in the past. It is a determination not to accept sin in the future. That change in mind then leads to changes in behavior. "For godly sorrow produces repentance leading to salvation, not to be regretted; but the sorrow of the world produces death. For observe this very thing, that you sorrowed in a godly manner: What diligence it produced in you, what clearing of yourselves, what indignation, what fear, what vehement desire, what zeal, what vindication! In all things you proved yourselves to be clear in this matter" (II Corinthians 7:10-11). But notice what you do: even while wanting to change, you know you are going to return to your past sins. Sin is prevalent and we can't live a sin-free live (I John 1:8-2:1), but it doesn't mean we accept defeat. "Therefore submit to God. Resist the devil and he will flee from you" (James 4:7). It is here I think you harm yourself the most -- you don't put up any resistance.
You have to take a no-compromise attitude. "No one who abides in Him sins; no one who sins has seen Him or knows Him. Little children, make sure no one deceives you; the one who practices righteousness is righteous, just as He is righteous; the one who practices sin is of the devil; for the devil has sinned from the beginning. The Son of God appeared for this purpose, to destroy the works of the devil. No one who is born of God practices sin, because His seed abides in him; and he cannot sin, because he is born of God. By this the children of God and the children of the devil are obvious: anyone who does not practice righteousness is not of God, nor the one who does not love his brother" (I John 3:6-10). This doesn't mean you will never mess up and sin again (remember I John 1:8, 10). It means the true Christian doesn't tolerate sin or makes excuses for it. If he sins, he corrects the problem because sin is not a part of his nature.
It isn't that you can't do something about these sins. You are able to overcome them. "No temptation has overtaken you except such as is common to man; but God is faithful, who will not allow you to be tempted beyond what you are able, but with the temptation will also make the way of escape, that you may be able to bear it" (I Corinthians 10:13). But I and no one else can make you change. You have to decide to change. All I or anyone else can do is encourage you and support you as you change.
So list out each sin, and decide what you are going to do differently so you don't fall back into each one. Not all will be successful, but continue to make adjustments and changes. Never accept sin, but find a way to strengthen yourself so sin doesn't have room in your life anymore.
This is something many people forget. Being a Christian is not just about getting rid of sin, it is also about filling our lives with good, so there is no room for sin in our lives. "Let us walk properly, as in the day, not in revelry and drunkenness, not in lewdness and lust, not in strife and envy. But put on the Lord Jesus Christ, and make no provision for the flesh, to fulfill its lusts" (Romans 13:13-14). Therefore, find better things to do with your time that you used to waste in sinning.