Luke 9:58,60,62 (NKJV)
And Jesus said to him, "Foxes have holes and birds of the air have nests, but the Son of Man has nowhere to lay His head."
Jesus said to him, "Let the dead bury their own dead, but you go and preach the kingdom of God."
But Jesus said to him, "No one, having put his hand to the plow, and looking back, is fit for the kingdom of God."
I don't think Jesus is talking about salvation here but rather being called to full-time ministry for Christ. The first answer was to a person who had not received a call from Jesus to follow but was expressing a desire to do so. Jesus in essence discouraged him by telling him what the costs were. The second and third times, Jesus had given a clear call to follow but the person was half-hearted in his commitment. Jesus makes it clear; commitment to Him comes before any other desire.
Becoming a full-time minister for Christ will be miserable if you have not received the call from God to do so. To do so would be to attempt it with your own power dooming the mission to failure without God. It is also a miserable life for the one who has received a call but wavers in his commitment. Blessed is the one who receives a call from Jesus and follows Him with his whole heart.