Train, an excellent post. You may want to add to that as well, that unless one has developed a "feeling" (even if sometimes it is wrong) for a stock (or a contract), not to trade such stocks (or instruments) exclusively. A good idea is to "spread the risk" in smaller chunk in each situation so that even a hard hit on one position does not "kill you". The worst enemy of a trader is his "mental attitude". You must go in there as a fighter battling the MM's and the specialists with an ego big enough to want to prove to "them" you are better. If you have tendencies to be "moody", step away from the screen until you are in a positive mood and ready to do "battle".
The best thing for a good trading day, is to have one or two small gains from the "let go", it kind of set the stage for the rest of the day. You already mentioned the importance to cut losses fast, but I just must repeat this, because the most important thing is to be able to come to the fight the next time around. If you have a loss, look in the mirror, say to yourself "I screwed up" NEXT...... last, but not least, PLAN THE PLAY AND PLAY THE PLAN.