Well
There are several places in the Bible that tell us to obey his commandments. Everything we do, we do in the name of the Lord Jesus. Jesus said if you love me you will keep my word. (Commandments) we know we are of God because we love other Christians.
Being lukewarm is a lip service Christian. They go to church, may even give money, but God is not first in their life. They conduct their life as if there is not God.
Moving to get a better Job without even praying about it and leaving a church God put them in. (Money first!!)
Keep the policy of not talking about Jesus at work.
Plan trips, and go places without even a thought to the will of God.
find churches based on their denomination and not where the Holy Ghost wants to lead them.
Have no idea what God's plan for them is. Don't make an effort to find out.
Jesus said if you will confess me Lord, then with the mouth salvation comes. People do this, but never even consider they have a Lord to consult with before making all kinds of plans.
Some have even used the authority of the name of Jesus to cast out devils and get people healed, but their heart is far from his will and plan. He told these people that he did no even know them.
So, Being a Christian means that Jesus Has to be Lord in everything!! even the money you bring in, we need to consider him first before any bill or things we want.
As for being a lukewarm Christian, Jesus was even more unhappy about these people because the profess him in word and not in deed.
So for him to spit these people out, and have him say I did not even know you, It would be really safe to assume that being with him in eternity is not going to happen.
Jesus Is Lord.