If you have come to a point in your faith where you are having to face the ugly reality that there often exists a serious gulf between what you intend on your best day and the poor decisions that you make on your worst, let me assure you, you are not alone. Let's look at a great example of this in Scripture. Peter was one of the disciples that followed Jesus the closest. He loved the Lord and served Him faithfully. He was a leader of men, bold, sincere and passionate, but like each of us, Peter was a work in progress. He was prone to emotional, even angry outbursts. He was proud and self-assured, arrogant and completely ill-prepared for the challenges he was about to face.
The night before Jesus was crucified, He gathered with His disciples to celebrate a very important passover meal. Towards the end of the evening, Jesus made a statement that alarmed everyone. He said, "Tonight I will be betrayed into the hands of my enemy and all of you will desert and abandon me". He then addressed Peter specifically, saying, "Peter I have prayed for you; when you have repented strengthen the others". At this Peter blurts out, "Even if all the others deny you surely I will not". Now let me ask you a question, do you believe that Peter was sincere in his statement? Did he really mean this? Did he fully intend on remaining faithful no matter what? I believe he was but as we have already established, there is often a difference between what we intend and how we act. Notice, Jesus did not just fix him. He did not do anything to prevent him from facing this trial. No, Peter would have to face this and through it grow into the person that God had called him to be. I assure you, this is a lesson Peter would never forget. I am sure that in his dying days, shortly before his own martyrdom, he reflected on this life lesson often. Jesus prayed for Peter and then left him in the hands of His Father. These events played out exactly as Jesus had predicted.
Luke 22:54 NIV
 Then seizing him, they led him away and took him into the house of the high priest. Peter followed at a distance.
The one that had followed him so closely now follows from afar or as the Message versions puts it "a safe distance".
Matt. 26:69-75 NLT
69 Meanwhile, Peter was sitting outside in the courtyard. A servant girl came over and said to him, "You were one of those with Jesus the Galilean."
70 But Peter denied it in front of everyone. "I don't know what you're talking about," he said.
71 Later, out by the gate, another servant girl noticed him and said to those standing around, "This man was with Jesus of Nazareth."
72 Again Peter denied it, this time with an oath. "I don't even know the man," he said.
73 A little later some of the other bystanders came over to Peter and said, "You must be one of them; we can tell by your Galilean accent."
74 Peter swore, "A curse on me if I'm lying--I don't know the man!" And immediately the rooster crowed.
75 Suddenly, Jesus' words flashed through Peter's mind: "Before the rooster crows, you will deny three times that you even know me. "And he went away, weeping bitterly."
He wept bitterly. He is sincerely repentant, brokenhearted over his actions, truly sorrowful. So what happened, how do we explain Peter's failure--our own failure? Like Peter, we find ourselves in this position of acting contrary to our heart intentions. Try as we might our efforts often fall short of our intentions. Jesus had warned him; Jesus even prayed for him. Please understand I believe that the answer surely is in the reality that Christ has set us free from the overpowering control of sin. In no way do I want to diminish the sacrificial work of Christ, the victory He has already won over sin. So why do we still sin? There has to be more. Dallas Willard says this about Peter, "All of his sincere and good intentions, even though specifically alerted by Jesus' prediction and warning a few hours earlier, were not able to withstand the automatic tendencies ingrained in his flesh and activated by the circumstances". We must understand that good intentions are not enough. We have relied on "trying" for too long. We must realize that there are latent tendencies, call them habits, that exist even after Christ has broken the power of sin in our lives.
Christ came to set us free from bondage to these ingrained tendencies or a hypocritical existence pretending to be something we are not. Christ did not bid us to come and follow Him and He would give us the appearance of transformation. No, He came to give this life to us in reality not just in theory. The Scripture promises that you will never face a temptation that is not common to man or beyond your ability to withstand. Indeed God is faithful and compassionate toward us and He promises to give us "strength of resistance and the power of endurance". He has promised that He will provide a way of escaping sins grasp. (1 Corinthians 10:13 AMP) Now whether we choose this path of escape or not is another matter. We have in fact, been given a certain victory over the power of sin. Peter was specifically warned and then given what I believe was a way out or at least a way through the temptation he was about to face. When Christ invited him to join Him in the garden for prayer, He was modeling for him a solution to combating these ingrained tendencies of his flesh. Christ was demonstrating that our battle with the flesh is not one that can be attempted with a frontal assault. He tells Peter that it is imperative that in the face of an imminent attack to be vigilant. He helps us to see how prayer positions us and prepares us for the battles we will most certainly face. Jesus tells Peter, "PRAY, pray that you do not yield to this temptation". Christ tells him what each and every one of us have learned, "The spirit is willing but the flesh is weak". The Message puts it this way, "There is a part of you that is eager, ready for anything in God. But there's another part that's as lazy as an old dog sleeping by the fire."
Jesus is trying to teach Peter how to weaponize prayer, how to use prayer as a discipline against the ingrained tendencies of his flesh that are warring against his spirit. Dallas Willard defines discipline this way, "Disciplines are, in essence, activities in our power that enable us, by grace, to do what we cannot do by direct effort--by 'just trying'." They are, "Necessary components of life with Christ--they are simply activities that we undertake, activities in our power. They are something we do that enables us to disrupt evil habits and patterns in our lives and receive grace to enable us to grow increasingly toward easy, routine obedience to Christ." Christ is showing Peter that the only way you can overcome the temptations you face in life is not through direct effort but rather by developing the spiritual character of Christ within you and by replacing the ingrained habits, failed responses and lusts with new ingrained spiritual character. There are simply no short-cuts. Without the cross, we would have no power to exercise over sin. But without spiritual growth and formation, we will never experience that power.