Using a pre-defined betting unit helps manage bankroll by establishing consistent, controlled bets, allowing players to minimize risk and avoid impulsive wagering. It sets a standard amount for each bet based on a player's total bankroll, ensuring they don't exceed limits, and helps prevent drastic losses during downswings. This strategy also allows for better tracking of wins and losses, helping players stick to their budgets and make informed decisions throughout the gaming session. Maintaining discipline with a set betting unit helps protect the bankroll over time.