My two cents, before I rush out the door.... Trading is very much like a contact sport. Infact, if I had my own way, no one will be allowed to trade until they have gone a few rounds in a boxing or MMA ring - wait what am I saying? ... then there will be no one to scalp!. I must be getting soft these days ...
Seriously though, if people were forced to go a few rounds in a ring before trading, it will render almost almost all books on trade risk management useless. One can only take so many jabs to the face and uppercuts to the chin before the hands instinctively go up when you ENTER the ring, and those damn hands won't come down until the round is over or the fight is over, i.e. until you are EXITING the ring. I really don't know why people make trading out to be such a difficult thing - maybe they are suckers for punishment?. I seriously believe that pain is a very useful learning tool for traders. I remember when I first started trading options I looked at all the sensitivity charts and understood it at an intellectual level. After getting seriously hammered by the market, I have an EMOTIONAL connection to the charts, when I see an ATM option near expiry with high gamma, I literally wince - because I know how devastating that can be to ones account.
Trading is like fighting, once you ENTER the market - ITS ON, and it dosen't stop until you have exited the position(s). If you did not do enough research about your opponent before you enter the ring, the flurry of hooks, jabs, overhand rights etc that will meet you will soon tell you that you should have done more research. personally, I don't like (receiving) pain, a nosebleed (i.e. a number of points loss) is enough for me to retreat and throw the towel in - so I can live to fight another day - AND you can bet your bottom dollar that the next time I ENTER the ring, I would have done my research THOROUGHLY. The rule for entry is basically this - do not wait for the market to prove you wrong (by that time, its too late). If the market dosen't behave as you anticipated shortly after ENTERing the trade, don't wait till the market suddenly moves 10 points against your position - you'd already been KO'd by then. Take, a small loss consistently and keep you powder dry so that you will be alive and full of "rude health" when the market is there for the taking.
Exits are also important, because you can still get clobbered on the way out. Again, its a case of choosing your battles carefully and running aware like a scared rabit if you need to. Basically, as they say in contact sports - "protect yourself at all times" - if you follow that advice (consistently), you will do just fine