1) go into every trade expecting it to be a loser, your job is to reduce the loss.
2) have a clear set of rules and follow them like a machine, if you cant and your rules are simple enough, try to get your trading activity automated to remove the emotional attachment. this could ultimately be ruining your performance if you dont trust what you are doing or what you should be doing and when.
3) increase your position as the market moves in your favour and continually do this for as long as it proves you correct (refer to point 1.), just know when to stop doing this and start with only a portion of the intended trade amount. This way you can assume that your minimising your losses and maximising your profits. I have recently found this to be very usefull as I can increase the amount of capital which is exposed to the market without increasing financial risk. thus netting me more profit when the market proves me right and losing less when the market decides it wants some of my capital back.
simply by implementing a strategy to add to your position can turn a system with a low win vs lose ratio into one which performs with a higher ratio, assuming the risk vs reward for the two systems are constant.
4) remind yourself you dont know everything in advance and you can only react to the market action.
if your getting emotional about a trade, its probably because you are trading too much, risking too much or have yet to accept that the future is uncertain, or combinations of these.