By "when things get hard in a trade", I think you mean when you are hanging on to what you would consider a big loser. That could mean a few things:
1. Your trade direction was wrong to start. Retracements tend to give you "hope" to hold on, but then the trade continues against your position. That could mean your method needs tweaking because you are trading against the main trend or you just misread the market.
2. Your trade direction was correct, but your timing was wrong...meaning you got in when the market was retracing, so you're losing because of it. Could mean that your entry criteria may need refining, or you need to pay more attention to the trend on the longer time-frames.
To answer your question...
To manage emotions, you need to be able to exit that "emotional state" by latching on to something more concrete...a more logical state. Emotions and logic can't operate at the same time, so you've gotta flip the switch. You can do so by going through the details of your method...begin thinking things through. Bring your focus there. If you can accurately assess what is going on (per your method), then you can make a better decision as to whether to hold on or bail...and bailing should be done as early as possible once you realize your trade is in the wrong direction.
If you feel that you cannot assess what is going on in the market correctly, maybe you should just exit, clear your head and take another look.
Overall, don't trade with large position sizes that would create such a loss, that things could get you to that point of a "hard trade" from the standpoint of enduring such losses. Reserve those "larger" positions for entry criteria that are what I call textbook set-ups per your method: where everything lines up. By the way, do you use stop loss orders?
Hope that helps.
FX4Newbies