I have been teaching people to trade for almost 10 years now, and this continues to be a problem for them.
My solution is this.
Buy low, sell high...we all know what this means.
What we need to include here is that it doesn't matter in which order you do it.
Sell high, buy low...that's the goal of going short.
Now, for some more detail about what "going short" on the forex is. There is no such thing, technically, as a short trade on the Forex.
In a currency pair like the EUR/USD, if you buy the currency than your are betting that the "pegged currency" (the first one in the "fraction"), or the EUR in this case, is going ot increase in value.
So, you are purchasing EUR with the intention to exchange it back into dollars when you get more $$$ back than what you paid.
On the other hand, when you "sell short" the EUR/USD, you are betting that the USD will rise in value, therefore sending the EUR lower in value.
In this case you are purchasing USD in exchange for Euros, and are betting that you could sell those $$$ back in return for more Euros.
See, that sounds so much more complicated and I hate it.
So, once again, the simple version.
Buy low, sell high...in whatever order you like.
I hope this helped...and good luck.