If I trade is going against me e.g. instead of going down, a reversal happen and trade goes up. Now If I Cancel/delete this trade, will have to bear the Loss e.g. My Balance is 600$, Equity is 580$. If i delete this trade then my New Balance would be 580$ or remain same i.e. 600$.
Same applies, when your position is filled (trade runs), you will have to bare the loss. However, when you have a pending order that is not filled yet, you can close it as it is not yet filled.