It’s no mystery why hikers in the midst of a grueling long-distance journey love trail magic. Whether you’re having a great day or feeling ground down, hot, cold, tired, or sore, an unexpected treat or random act of kindness by a stranger — food, a ride to town, sage advice, a clean privy — can provide an instant jolt of joy and gratitude. But here’s a secret: The people who provide all that generosity and serendipity will tell you that they get just as much out of it as hikers, ...