In the quote, the speaker reflects on youthful ambitions to become a genius, which is a common aspiration among young men. However, they acknowledge that this goal was humorously challenged by the reality of life, implying that such ambitions might be overly idealistic or unrealistic for most.
The phrase "mercifully laughter intervened" suggests a recognition that humility and humor save individuals from the vanity of overestimating their abilities. It highlights the importance of humility and the role of humor in keeping expectations grounded in reality.