This is an eternally true adage in the field of business because if a businessman does not take ricks in the business he will never be able to profit from the business.
However in trading and investing you must not only just mindlessly taking risk but also taking calculated risk depending on the current market situation or sentiment. Your main goal in this market is to win more money than you lose it. Because you cannot avoid losing but you can minimize it. You also have the control to be able to hold in losing position until proven wrong and not be fearful when market is in worse certainty. Yes taking risk is essential. But managing it with the best of your ability is what will set you aside from the rest.