This is particularly true of the main twelve. Of them, only John is supposed to have escaped martyrdom and died a natural death. Being a follower of Christ, especially in the early years of the Church, brought persecution, punishment, and often death. One would have to hate one's family to put them through that. One would certainly have to be ready to die.
Jesus goes on to talk about builders and military leaders needing to make certain of themselves before they commit to a plan of action. Honestly, when looking at what was asked of Christ's disciples in the past, I do not know if I am strong enough to be up to that task. In truth, I don't believe that anyone is on their own. This is where trust in God is so important to our lives, and so important to our souls. Through Him, all things are possible.