When I was in college my fraternity went on a trip to a local state park, known for its huge cave system. At the time, the caves had not been explored and certainly not opened to the public.
It was not surprising to find a huge maw smiling from the side of one of the hills we were hiking on. We were adventurous college students, so we decided to enter the cave mouth, but as we walked upright into the shallow cave the ceiling began sloping into the hillside causing us to have to stoop, then crawl. The room-sized cave turned into a small tunnel that, at its smallest, required us to squirm on our bellies.
That experience may be what caused me to become clautrophobic. Squirming through the cave in total darkness required a determination and focus that we did not expect when we walked, standing, into the cave mouth. Nor is it what you expect when you embark on a discipleship with Jesus.
Which is probably why Jesus warned a wannabe disciple that following him would require the most rigorous sort of devotion. Squirming on your stomach in total darkness at times. Discipleship and cave exploring are not for someone who gives up quickly or who has no stomach for difficulty.
At the conclusion of the Sermon on the Mount Jesus said that the road that disciples take is arduous and not easily navigated. Things worth having or experiencing are rarely easy, and many people are not willing to start the hike.