All fund managers have a system. Some have it in their gut and head while others code it into a computer. After coming to terms with a system, the manager must follow it religiously in order to maximize results and perform within investor expectations.
I believe the main reason why benchmarks outperform managers is due to their lack of discipline.
Medium post: https://medium.com/@mmelissinos/the-occasional-mistake-b1d02926fb95
17: The Occasional Mistake