Large crowds were travelling with Jesus, and turning to them he said: “If anyone comes to me and does not hate his father and mother, his wife and children, his brothers and sisters—yes, even his own life—he cannot be my disciple. And anyone who does not carry his cross and follow me cannot be my disciple.
“Suppose one of you wants to build a tower. Will he not first sit down and estimate the cost to see if he has enough money to complete it? For if he lays the foundation and is not able to finish it, everyone who sees it will ridicule him, saying, ‘This fellow began to build and was not able to finish.’
“Or suppose a king is about to go to war against another king. Will he not first sit down and consider whether he is able with ten thousand men to oppose the one coming against him with twenty thousand? If he is not able, he will send a delegation while the other is still a long way off and will ask for terms of peace. In the same way, any of you who does not give up everything he has cannot be my disciple.
“Salt is good, but if it loses its saltiness, how can it be made salty again? It is fit neither for the soil nor for the manure pile; it is thrown out.
“He who has ears to hear, let him hear.”
Luke 14:25-34 (NIV)
I strongly recommend listening to Peter Jensen’s address to CMS Summer School (2007) on this passage.