Paul reminds the church of Corinth where their attention needs to be in order to avoid spiritual deception. If they get their eyes off of Jesus or look for a source of truth that is less than His Word, they will happily deceive themselves and wander everywhere but the truth.
The most common source of spiritual deception is us.
Pride is a false view of ourselves and others.
Your vulnerability to deception is directly related to your proximity and dependence on Jesus.