So, because you are lukewarm–neither hot nor cold–I am about to spit you out of my mouth.
The metaphor exemplified by being hot or cold demonstrates whether or not one is a believer or a non-believer. Whether one is pure or whether one is sinful. Whether one is saved or wicked.
The mouth represents heaven.
We all at one point have walked up and down a flight of stairs. But focus your attention on that one step. If we tried to walk on the angle of that step we would be out of balance. One foot to the left to catch our balance (Believer, Pure, Saved), and often our other foot to the right (Non-believer, Sinful, Wicked). As we attempt to balance ourselves between light and darkness within our indecisiveness Christ tells us that such an individual who is confused with the commitment of His ways is just as bad as someone who refuses to commit to His ways and therefore will be spit out.
The best way to rid ourselves of such confusion is to dig deep into the love of God and follow through with daily scripture reading. To embrace the opportunity of Heaven by committing our lives to be lived as believers who are pure and saved.