It is not human vs. human sports, you play against nature. For some fishermen, going after the fish means their challenge. They catch fish and accomplish the part of nature. They can't forget the feeling of catch a fish and challenge and thrill. This quote is using and talking about fishing as a example, but you could say this quote is talking about everything around us.
Many people go try something without knowing the stuff they are after.
This Grand Canyon trip wasn't an easy thing. I had a lot of times that I thought I would not make it. Especially on the way to the camping place. It was hot and tiring. Just walking the trail down just looking at rocks wasn't very fun.