It depends why you are having losing trades. If you are applying your system by your rules then by definition of probability trading you do not cut back and you do not stop trading. Remember, or if you can't remember this you should know that each trade has a random outcome, however, over a series of 100 trades or some larger sample, your edge gives you a higher probability of making money in a larger sample size.
Many traders make the mistake of not following their system because of a string of losses. Profitable ways of trading all have losses, and no system will tell you when they will happen, in what order, or if they will be all in a row or spread out. Then only thing you really know is that over time your edge gives you a consistent opportunity to make money.
You must take every trade that conforms to your signal of a valid edge. If you cut back becaus you lost, and you followed the rules, you are now screwing yourself out of the inevitable winners that your last lost just brings you that much closer to.
If it is a discipline problem, then something is broken and you should fix it or you will just lose money and no strategy will fix that. If this is the problem, then your real work is just beginning, my friend.
A casino operates the same way. They must take the other side of every bet, every time. They know that they will pay out some big winners (a large loss for the casino), they will make out big on a few gamblers, and make more on average because of their edge. But they take the bet every time the opportunity presents itself. (see Mark Douglas, Trading in the Zone).
You must trade like the casino, and take every edge, every time. Given that you operate within your risk parameters. Trading is simple. If you are not operating by your rules, either you have some internal conflict, or maybe you hate your rules, and have to adjust them. If you adjust them, test them. But set up rules and follow them. Trust me, I have been on both sides of that fence, and constantly monitor myself for which kind of losses I am having too.
One other thing, sometimes you can be disciplined and just be plain tired of trading. This is a signal too. NOthing is wrong with your strategy, you are not crazy, but you are tired and need to rebalance your life. Maybe go snowboarding or take your kids or girlfriend somewhere nice with all the disciplined money you have made. This is my biggest area. Doing well then just getting a little tired of the grind, and I have learned to try to seek excitement outside of work.
Hope some of this helps.