We are of God. He who knows God hears us; he who is not of God does not hear us. By this we know the spirit of truth and the spirit of error."
1 John 4:5-6 (NKJV)
Have you ever met someone who seemed disconnected from the world around them? Maybe the other person was talking on the phone, or texting someone, or listening to some music and they don't even seem to notice that you are there. You could say that because this other person is so caught up in something else that they are in an alternate reality and they are not really aware of the world around them. This person is more connected to their alternate reality than the world that they live in.
Jesus told the Pharisees in John 8:23 that He was "not of this world" and in John 18:36 that His "Kingdom is not of this world". While Jesus was living in this world, He did not identify Himself with what was happening in the world around Him, but instead Jesus was focused on His Heavenly identity. This does not mean that Jesus was totally unaware of what was going on in the world around Him, but Jesus had more of an eternal perspective than a natural one.
Just like Jesus, we need to live in the "alternate reality" that we are citizens of Heaven (Philippians 3:20) and that our true identity is in Christ (Colossians 3:1-3). Of course, we should not totally detach ourselves from this world and ignore reality so that we are not aware of what is happening around us, but we need to keep our focus on spiritual things and not earthly things. It is easy to get caught up in all the things that are happening in this world, but our real life is in Christ and that is the "alternate reality" that we need to live in.