If you look at things as simply as you possibly can, there are only four situations that the currency pair can be in. It's either in a downward trend, upward trend, sideways trend, or a reversal. Even though were looking at these charts, there are only two ways the price can go; up or down. The best analysts in the world look at any point on any curve and they realize there's a better than fifty percent chance that it'll do the one. The lousiest analyst in the world would believe that at any time you have a fifty-fifty chance of winning. In a downward trend you have a less than fifty percent chance that it will immediately go up. In an upward trend you have less than fifty percent chance it will immediately go down. Reversals look no different from take profit lulls until they get big.
The fact is that we should all 'pretend' that we have a less than fifty percent chance of being right. That means risk to yield ratio, and risk to account balance ratio. If you use a 1:2 risk to yield then if you're right once out of three guesses then you'll stop losing money. If your risk to account balance is 1:10 and you go through a losing streak and lose 19 trades in a row your loss would be over 85% of your account! If your risk to account balance is 1:50 you would have a 30% loss of your total account. I like 1:100.
That doesn't mean that you can't lose on trade number 20, and it doesn't mean you can't get forty winning trades in a row either.
You should also know that some people use a strategy like 'double down' in blackjack. The purpose is that if you have a high chance of winning you should take the opportunity to increase your bet. I staunchly disagree with any increase in your bet by any more than double, and any time you go to 1:10 I think you're being a sucker. Unless you're betting on death, taxes, or an uninformed inadequately educated forex trader losing all of their money.
Lastly, in business, there's only one way to fail, and that's quitting.
That said, I also recommend trying to give your deals a chance even if they're looking sour. If you make a move and bail at the first sign of trouble there's a bigger chance that you'l be bailing more than collecting.