There is risk in every trade, you just have to find it

 "And now I'm gonna tell you something even more important, right? Don't you ever f***ing tell me, in your whole f***ing life, that there's a trade that doesn't have a f***ing risk in it, OK? That's what those **** over in Credit thought and look at what the f*** happened to them.... And you should probably go back to your seat now and have a good long think about what all of that means. And you make sure its the last f***ing time you ever do a trade that you don't know the risks of"  - from The Trading Game by Gary Stevenson 

Well, it could have been said more politely, but the thought is correct. Every trade, every asset has risks. Return does not come for free. It is your job to know what are the risks. 

While the book is a sometimes good read, it may not be completely true. See Gary Stevenson claims to have been the best trader in the world. His old colleagues disagree