In the Corinthian letters, Paul warned them NOT to ever leave the simplicity that is in Christ. We have one supreme responsibility as a believer, and that is to abide in Him. In John 15, Jesus used the analogy of a vine and branches. A branch is absolutely useless, unless it is connected to the vine. Separated from the vine, the branch is dead, unable to produce "anything".
That is why in Hebrews 12, as we run the race of faith, the call is to fix our eyes... NOT on the law, NOT on principles, NOT on a creed, but on Him alone, for He is not only the Author of our salvation, but the Perfecter of our salvation as well.
Anytime, we fix our eyes on anything other than Him, we will forfeit the simplicity of Christ for complexity. Anytime, we fix our eyes on anything other than Him, the emphasis of our lives will be on that "other thing", and ultimately on how we are doing pursuing that "other thing"... and we will end up with a man-centered Gospel instead of a Jesus-centered Gospel...
... and that will be no Gospel at all.