I once saw a report on the discovery or history channel that told the story of a huge flying dinosaur who was relatively old and lived somewhere in South America. When mating season approached, he migrated all the way from there over Canada to the south of Spain. When he arrived he saw thousands of his kind mating, but no female took any interest in him, so he died there of a broken heart.
I saw this story many years ago. Given that I still remember it, it must have left quite an impression on me. Another sad story had a similar impact, which supposedly took place a few centuries ago in France. When a family man couldn't take the company of his father anymore, he threw him in a rage out of his house and pulled him by his hair out of the cottage. Suddenly the old man cried "No, not any further - it was here when I let my father go".
You will say that these stories should not scare the spiritual path traveler. We have conquered our sex drive so we are unlikely to travel in old age from Argentina to Spain only to be laughed at by the object of our sexual passion. You will also say that we are mindful enough not to live in a dog-eat-dog social or professional environment, and what we don't do onto others, others are unlikely to do onto us. But what about the lingering fear of not reaching enlightenment? No amount of meditation or spiritual contemplation can get you to samadhi. We all know that the last step happens by the grace of the Source. The only way to overcome this fear is to stop searching, isn't it?