Bankroll management
A set of rules for managing trading capital: how much to risk per trade, when to stop and how to protect the bankroll from losing streaks.
Bankroll management (or money management) is the set of rules that defines how you handle your trading capital. By far, it is the factor that most separates those who survive in the long run from those who blow up the account — even more than the entry strategy.
The core principle is risk per trade. Most professional traders risk only 1% to 2% of the bankroll on each entry. That way, even a bad run of 10 losses in a row does not destroy the account — there is capital left to recover. Risking 20% or 30% per trade, by contrast, turns a normal losing streak into ruin.
Other essential rules: set a daily stop (stop trading after X losses in a day, avoiding the emotional loss of control known as tilt), keep position sizing constant instead of raising the bet to "win it back", and keep trading capital separate from everyday money.
Bankroll management is the direct opposite of strategies like the Martingale, which double exposure after losses. While the former protects capital so you can stay in the game, the latter concentrates risk and sooner or later leads to catastrophic losses. Discipline beats excitement.