1. Discipline in day trading means that one should be trading as per a trading plan or system.
2. Discipline further means that one should be able to avoid trading on the basis of hunches or emotions.
3. One should book profit as per the pre-determined plan and should avoid taking the impromptu decisions.
4. Discipline encourages one to book a loss when the need arises and same be executed ruthlessly as per the prevalent trading plan.
5. Avoid over trading and the times when market tells you to relax and not to trade.