In his parable of differing “soils” Jesus specifies some of the reasons certain people initially embrace Christianity, often with a great deal of enthusiasm and fervor, but then after a while bail out never to establish a root system which bears genuine and lasting fruit. Those identified as the first to leave do so because of “a time of testing” (Luke 8:13). This is some kind of painful situation or “persecution” (Matthew 13:21) that arises in a person’s life because of his or her new alliance with Christ.
This is easy to imagine, knowing the power of social pressures and the unsympathetic “friends” who are quick to disparage and ridicule one’s confession to follow Jesus. When Christ costs friendships, some new “adherents” of Jesus are quick to say “forget it”. The other primary reason is variously described as “the cares of the world” (Matthew 13:22), the “pleasures of life” (Luke 8:14), or simply a “desire for other things” (Mark 4:19). The assortment of worldly attractions will certainly put one’s supposed faith to the test.
Time will reveal whether people who claim to “follow Christ” will actually experience a God-given consistency in following Christ, or will instead retreat to following their own cravings for the temporal things of this world. So, without being cynical, we must be cautious knowing that based on Jesus’ teaching, not every “I’m for Christ” is genuine.