We know that the market is dynamic,as in it changes constantly,and as such,an investor who isn't careful enough to know when he is investing will fall in to heart problems or emotional trauma as a result of a massive fall in value,that is why it is important to condition your mind in a way that you won't get heart failure when you are at the loosing end.
Every investor knows there is risk in the game,and taking the risk is what shows you are ready to eradicate poverty from your life.
I think before venturing into any business at all especially trading, one has to know what is involved. Right from the beginning you're warned that trading is risky and you should invest what you can afford to lose.
With this alone you don't need to be told that there's a possibility of losing your investment. The best strategy is to maintain that standard of investing what you can afford to lose. This way, you will save yourself from heart attack if you eventually lost.