What I'm saying is that we have to always remember that though we are saved and know it, we have the potential to allow our desires to overtake us and cause us to leave a perfect standing in the eyes of God for an perfect standing in the eyes of the world. Think about an example...
He's one of the most well known, and yet most misunderstood, men of the Bible. He was an apostle of Jesus Christ (1 Peter 1:1), he was a fisherman by trade (Luke 5:8), he often stuck his foot in his mouth not realizing the magnitude of his statements (cf. John 13:8, Acts 10:14) but he was also one of the most courageous men that I read about in the Scriptures!
Facing what could have been up to 1000 Roman soldiers, the creme of the crop when it came to military force in the 1st Century A.D., (John 18:3) Peter was willing to fight for his and his Lord's life regardless of the circumstances (John 18:10). And yet, just a few hours later, Peter would be forsaking the Lord even to the point of using profane language to nail his denial home (John 18:15-18).
I hope that I can say that I would be willing to fight up to 1,000 men for my faith armed with nothing more than a sword and a heart, but I don't know if I could (facing situations often changes the way we act from the way we say we would act). If Peter was able to have that amount of courage and fortitude and yet just a few hours later was turning to his own vomit (cf. 2 Peter 2:22), what does that have to say about our chances of giving up without really realizing what is happening?
Don't get me wrong, I'm not saying that those of us who fall victim to our own lusts and leave are doing so in a defiant, "I'm leaving the church" type of attitude. What I'm saying is, it can hit us without even realizing what has taken place in our spiritual lives.
It's rather simple to say, but very difficult to implement. The only way to keep this from establishing a foothold in our lives is diligence. Paul wrote it best when he, by inspiration of the Spirit, said that we ought to constantly exert all we have in order to show ourselves as faithful and one that is approved by the Almighty (2 Timothy 2:15). He even wrote that we should do so in order to maintain the unity which only comes from an understanding that there is only one God-approved organization lead by the Spirit with the hope of eternal life and redemption in Christ; a group which follows the authority of the one Lord of the Universe, practices the one faith established by that Spirit and Lord, has only one avenue of entrance and worships the one Deity that is truly in existence (Ephesians 4:3-6).
See, easier said than done. But, it is within our grasps! If it weren't, we wouldn't be commanded to do so. The only catch is that it will take all that we have to reach the goal.
You want to know how to keep yourself from leaving the church? Empty yourself and fill your life with Christ. Then and only then will you be able to stand against the deceitful temptations of Satan and be approved by God at the Last Day (Ephesians 6:11, 2 Timothy 2:15, 2 Corinthians 5:9).