1. Placing a limit order in and then leaving the screen and not canceling the limit when you wouldn’t want it to be filled later or some news might come out and get you elected when the real prices is a fortune worse for you
2. Not getting up or being in front of screen at the time when you’re supposed to trade.
3. Taking a phone call from an agitating personage, be it romantic or the service or whatever that gets you so discombobulated that you go on tilt.
4. Talking to people during the trading day when you need to watch the ticks to put your order in.
5. Not having in front of you what the market did on the corresponding day of the week or month or hour so that you’re trading for a repeat of some hopeful exuberant event which never happens twice when you want it to happen.
6. Any thoughts or actual romance during the trading day. It will make you too enervated or too ready to pull the trigger depending on what the outcome was.
7. Leaving for lunch during the day or having a heavy lunch.
8. Kibbitsing from people in the office who have noticed something that should be brought to your attention.
9. Any procedures that violate the rules of the British Navy where only a 6 inch plank separated you from disaster like in our field.
10. Trying to get even when you have a loss by increasing your size and risk.
11. Not having adequate capital to meet any margin calls that mite occur during the day, thereby allowing your broker to close out your position at a stop while he takes the opposite side. What others do you come up with?
Speculation by definition requires some amount of loss otherwise the game is fixed. However, I believe loss can be broken down into avoidable loss and unavoidable loss. Unavoidable loss is, well, unavoidable. But in my personal experience (and based on pretty much all speculative loss I have seen or read about) all avoidable speculative loss is traced back to some core elements/violations: not being disciplined (many interpretations), getting emotional and all of the associated errors and mistakes that brings, sizing positions too big so that regardless of odds you eventually have to reach ruin, not being consistent in your approach (the switches), not managing your risk adequately either via position sizing or stop losses, finally you have to be patient for the right pitch whatever that may be for you.