First off, someone said the image to the left is a "weak" analogy because you can't "become" a car... but that's not the point - the point is that you don't "become" a Christian simply by standing in (or sitting, or going to) a church.
This weekend started off the new series "Life Apps" at church, and the sermon was about applying the word to our lives. Many people just "go to church"... and we deceive ourselves by thinking we can just listen in church and that's the end. The Bible was written to guide us in our walk with Christ - while it is not the "final answer", and the true answer is within ourselves, we can't find that answer if we don't apply Christ's basic principles to our lives. Many of us do this naturally, but it doesn't come so easy for all.
A relationship with Christ is a road to self-discovery - but by learning and applying the lessons of the people who came before us (learn from the past, from history) we can save ourselves a lot of time and grief instead of learning the hard way.
Being a Christian is not about keeping up appearances by attending church every week. Being a Christian means to follow Christ - to let him live in and lead your heart. Christ came to earth to save us, but also to set the example we are supposed to follow on how we treat others. In fact, when Christ came to earth and died for our sins, he saved us from the old law, and brought a new covenant that changed the "physical temple" (or church) to our hearts and bodies as the temple of God. So going to a physical place does not make you a Christian.
The key here is to learn the word on your own accord and to apply it to your life. To act on what you hear, and to put your faith into action. You can learn all the right words, know the bible inside and out, but until you do something about it, talking about faith doesn't indicate that you really have it. (James 2:14) God-talk without God-acts is outrageous nonsense. (James 2:17)
"Anyone who sets himself up as “religious” by talking a good game is self-deceived. This kind of religion is hot air and only hot air. Real religion, the kind that passes muster before God the Father, is this: Reach out to the homeless and loveless in their plight, and guard against corruption from the godless world." James 1:26-27