"for the kingdom of God is not eating and drinking,
but righteousness and peace and joy in the Holy Spirit. "
The kingdom of God is internal, not external. It's not the outward things that we do or don't do that make us a Christian, but the acceptance of the the finished work of Christ on the cross. By this we are justified by faith, and Christ's righteousness is counted as ours. It is a free gift that we cannot earn. It's given to us by God's grace. When we are reconciled to God through Christ we gain peace with God and the peace of God. Peace with God means we no longer struggle against Him, but now are cooperating with Him. The peace of God means we have peace within ourselves, knowing that we can trust God at all times. Through every trial we know that He loves us, that He cares about us. And this gives us joy. Even if we lose everything, we can never lose God's love. He is ever present and this should cause us to delight in Him.