Contemporary English Version (CEV)
Some time ago, Rachel and I were driving along the road in Kona where they do the bicycling portion of the Ironman. For 112 miles, they cycle along a barren stretch of road in a landscape devoid of warmth, surrounded by hardened volcanic rock. To complete such a feat successfully (and then, by the way, run a marathon after), you have to train. You have to sacrifice, and you have to work for years, but I imagine most of the people who finish say that it is worth it, no matter how hard it is. They could never have experienced the exhilaration of finishing without the work.
In the same vein, Jesus doesn't pretend that discipleship is easy, but he also paints such a compelling picture that the disciples believe it is worth it. To who else would they go? He, and He alone, is the path to eternal life. There is no other way, and if one wants eternal life, they must go through the Son to the Father. It is not easy, and anyone who says it is will be lying to you, but it is ultimately worth it to experience the joy of eternal life that comes through Christ the Son. We have faith, and we persevere, because the prize is worth the price.