That's where you need to be a little, "creative" ...In other words, fudge a bit...
1. Either stay on till protective stops are hit/next signal comes...
(I FAVOR this way because then you only miss out on taking profit on itty bitty trades, I want to catch the full 300-2,000 pips

)
b. take profit if it pays the rent/groceries/porn habit...er I mean prostitutes, that's an unofficial rule too, hehe <
Or
2. Exit at profit when you think time is the time is ripe. VERY subjective...not a good way to trade, unless your profit is 2-5 times greater than your avg. loss, then it's fine.
The price cross works, but to take out a bit of noise, one can throw a 5 or 10 SMA up for the cross of the 500 SMA...
Usually, you should take every signal and just follow it religiously. That way you don't miss the major break out...
Trading for the sake of trading will make you TONS of money...because you're not exiting early trying to pick a sweet spot...
The pigs sucked up the eur/usd in early december, and they kept buying..that's why u need to hang on to your trades until an opposite signal hits you in the head...
that also means 100 pip draw downs...so you must trade in the smallest size according to your account...no crazy "All In" moves..this aint - No Limit Hold Em' Fellas
If you trade small and know what's happening, you basically wouldn't need stops. You take the next signal and reverse your trade.