Discipline
Discipline is not just the ability to develop a trading plan and to stay with it; it is also the ability to know when your trading plan is not working and therefore, knowing when to abandon it.
Discipline is also the ability to give your futures trading positions sufficient time to work in your favour, or for that matter sufficient time to work against you.
Discipline is the ability to trade again once you have taken a loss. Discipline is the ability to ignore extraneous information and to avoid inputs which are not related to the system you are using.
Discipline is the ability to maintain reasonable position size and to avoid the motion which leads to over trading.
Discipline is the persistence required to maintain your trading systems and to calculate the necessary timing indicators consistently during the day, either manually or by computer.
Above all, however discipline is the ability to come back to the trading area every day, regardless of whether you have won, lost or broken even the day before.