I's sorry about your loss. Similar things have happened to me more than once. The most common mistake that I used to make was forgetting to cancell limits or stops. Ironically, on my experience, eventually almost all of the forgotten and then executed stops ended up with profits and almost all of the executed limits ended up with losses.
The easiest way to deal with such situation would be to have some simple rules to follow on a regular basis.
My rules are:
1. I almost always (99% of trades) place a stop before an actual position is taken.
2. When I place both a limit and a stop for a new position I always place the stop first and then the limit.
3. If I need to cancell them I always cancell the limit first and then goes the stop.
4. When there is a need to adjust stops I place new ones before cancelling the old ones. (Your case).
5. If those rare cases when I have a position but don't know to where to place the stops yet, I still place some protective stops at the level that would seem out of reach to me at the moment. Usually not more than 100-150 pips away from the current market price. So far it works well just for additional protection.
The easiest way to deal with such situation would be to have some simple rules to follow on a regular basis.
My rules are:
1. I almost always (99% of trades) place a stop before an actual position is taken.
2. When I place both a limit and a stop for a new position I always place the stop first and then the limit.
3. If I need to cancell them I always cancell the limit first and then goes the stop.
4. When there is a need to adjust stops I place new ones before cancelling the old ones. (Your case).
5. If those rare cases when I have a position but don't know to where to place the stops yet, I still place some protective stops at the level that would seem out of reach to me at the moment. Usually not more than 100-150 pips away from the current market price. So far it works well just for additional protection.