But his spirits that night were high as he looked down at the Colorado River.
"Being alone, in the dark, on top of the Grand Canyon . . . I was just kind of taking it all in," he said. "It just felt like a really special moment."
The allure of the open road has been tugging at souls forever.
Forsthoefel, now 24, said he took to the road on foot for a simple reason: to listen.
He talked to strangers young and old, collecting 85 hours of sounds and conversations.
And on Sept. 8, 2012, after nearly 11 months of walking, he plunged into the Pacific Ocean at Half Moon Bay, outside San Francisco, as family and friends looked on from the shore.
Since then, Forsthoefel, the listener, has become the one dispensing advice. Life, he found, is "all about people. It's all about us and appreciating who we are and what we have to share with each other."
It is the message he has delivered to audiences at several colleges and high schools, including West Chester University and his alma mater, St. Andrew's School, in Delaware. At those same events, he shared photos and recorded clips from his journey.
While debriefing from the trip, Forsthoefel moved to Woods Hole, Mass., to work on a radio essay, which was broadcast on the popular program This American Life in May. The town has become home for him. He will begin a part-time teaching assignment there next year, he said, and is working at a coffee shop while writing his book.
The change of pace has been jarring at times, he said, and the opportunity to share his journey with so many has been "surreal."
"I think there will be a time where I think, 'OK, I may have to go out again,' " he said. "The walking thing did feel like a big shot of something, so I don't know. The time might come again."
Forsthoefel's walk started in September 2011, a few months after he graduated from Middlebury College in Vermont.
His mother, Therese Journlin, said she had always known Forsthoefel, the oldest of her three children, would need to take a journey of some kind. At 10, she said, he would tell her he was going to jump onto a train, or take a trip to Peru, or work on a farm in Ireland.
"It was very clear he'd have to do something that challenged himself," she said.
Still, she said, when he finally set out on his walk, it was hard for the mother in her to let him go.
"He was 'on purpose,' and that was good," she said. "And if it meant I wouldn't see him again . . . I had to own that too."
When Forsthoefel set out, he said, he was unsure he would make it to the Pacific, or if he even wanted to. His immediate concern was heading south, since winter was approaching.
He stayed with a few family friends at first, but ultimately ended up finding people to take him in for the night at convenience stores, coffee shops, bars, and the like. If no one was around, he would camp out, he said. He would walk varying distances each day, sometimes more than 35 miles. He withdrew about $1,000 from his savings during the trip, he said.
At some point in Virginia, he said, he fell into a routine: The days were filled with solitude as he walked through sun and rain and cold and heat. He walked without an iPod, but he occasionally sang to pass the time. He picked up the stroller in Texas, when temperatures started to rise.
As evenings approached, he would try to find a place to sleep, making acquaintances and falling into conversation.
Many memorable moments came from taking in his surroundings, he said: seeing the Sierra Nevada Mountains rise after trekking through the desert, or walking through the bayou and moss of Louisiana.
But the best moments, he said, came when he interacted with others, as when a man in Alabama cooked him fried squirrel for breakfast, or when a couple in Maryland took him to their band practice at night.
When he started walking, he said, he felt "a potent mix of intense fear and sadness and euphoria all mixed together." He was unsure where he was going or when he would stop.
But by the end, he said, the journey of each day became routine.
Now, as he works at a coffee shop and writes his book, he had been able to reflect on what he learned.
"You can easily get the sense that we live in a pretty terrible world," he said. "That is not what I saw walking across this country."
Contact Chris Palmer, 609-217-8305, firstname.lastname@example.org, or follow on Twitter, @cs_palmer