Arjun was the best performing archer during the war of Kurukshetra. After the war, Shri Krishna asked him to safely drop Gopikas to their home. During their way back, the convoy was attacked by bandits in jungle. Arjun was defeated and his entire convoy was looted.
Though Arjuna was the best performer during the war of Kurukshetra, he could not deliver the same performance during his encounter with Bandits.
Similarly, today’s best performing mutual fund may not deliver the same return in future.