When I speak of leaving the gospel, I am speaking of leaving Christ, for Christ and the gospel are synonymous. If one loves' Christ, he loves the message of Christ, although one can love good preaching but not love Christ. Why do some leave the gospel which they professed to love once? The simple, answer is in the question, for if one truly loves Christ, then they will never leave Christ and His gospel. "Love never faileth."
When someone leaves the gospel, it is usually by degrees. They usually do not leave' suddenly, but begin to show signs of leaving (much like one who leaves his spouse). Unless that person is an out and out hypocrite, it is something they do not plan, but unwittingly overtakes them (as well as surprising everyone else, for quite often it is a long time member who leaves). You see, "the heart (of an unre-generate person) is deceitful above all things, and desperately wicked: who can know it? (Jer. 17:9). One can actually believe (in the head) and feel much emotion for the gospel for a time; even be convinced (deceived) that they love and need it, but time is the great revealer of us all. Because, THE HEART is the seat of true religion; because THE AFFECTION of the inner man is what determines a true be-liever and lover of the gospel, so the absence of that true love and affection will eventually cause that person to leave. And the other hand, true love prevents one from leaving. Let me illustrate:
If a man truly loves his wife, he doesn't need to consult his marriage license (as some do their baptism); he doesn't need to prod himself to go to work to support her; he doesn't need to force himself to spend time with her (rather than his buddies); he doesn't need to constantly go to meetings to remind him to be a "promise keeper" to his wife; he doesn't need to be constantly reminded by someone that he needs to be at home with her, he doesn't need to be told to buy her things. The fact is, if he truly loves his wife, these things will come naturally, from the heart.
If a man truly loves Christ, he doesn't need to constantly prod himself to hear the gospel, or spend time with God's people, or give to support that gospel he loves and needs. If a man truly loves Christ, his life is spent in service and enjoyment of Him. Leaving Christ and His people is not a possibility for the true lover of Christ.
Worship becomes a duty and a drudgery to the one who is about to leave the gospel. They attend the hearing of the gospel, not out of true desire, but for feelings of guilt if they do not. One is about to leave the gospel when it no longer touches them or moves them, when they are most often dull in hearing it, rather than lively as they once were. One is about to leave when they look for things to excuse them from worship or fellowship; especially when it involves spending time with people of the world rather than the saints. It starts with a gradual staying away (Wednesday nights, Sunday nights, Bible study), and grows in frequency. It begins with that person showing no desire to be with or fellowship with God's people (out the door in a hurry after services, seldom talking to anyone). It especially shows itself to the preacher, as he looks into a face that once lit up with the sound of the gospel, but hardly lights up at all now. It shows itself in the conversation of the one about to leave, for they become more prone to talk about other things than the gospel, seeming to only have their mind on the things of this world.
How often have you heard the preacher say, "We do what we want to do, and go where we want to go and who we want to go with:" If one truly loves Christ and His people, then Christ and His people will be his life. You can't run that person off. But if one does not truly love Christ and His people, then nothing you do or say will keep them. This is why you will not find this pastor running after folks who leave. The preaching of the Word is the only effective counsel.
This is a sobering verse to consider, "They went out from us, but they were not of us; for if they had been of us, they would NO DOUBT have continued with us: but they went out, THAT THEY MIGHT BE MADE MANI-FEST that they were not all of us" (I John 2:19). In other words, this all happens in order for God to expose some as the hypocrites that they really are and cause His people to exam-ine themselves. The real embarassment and shame for those who leave, will be before God 'someday. The "worm that dieth not" will be the memory of a gospel forsaken. Unspeak-able anguish will be theirs upon seeing true believers enjoying the eternal reward of the gospel, while they are left out. All due to their own foolishness.