A quick gander at the Heisenberg uncertainty principle may convince you that events and people around us are inherently unpredictable. Your reaction may be, “What is the point of my efforts?”
Luckily, we humans are irrational. Use that irrationality to your advantage, and your reaction will be, “I must try anyway.”
Thus you will use the Heisenberg uncertainty principle as a mere data point, and not as a fatalistic decision taken for us by nature. Perhaps a lack of understanding and inability to change perspective is the reason for all cynicism we see around us.
Upon further reflection, you will realize that human irrationality is merely a variation of the Heisenberg principle. Thus the advice to try anyway has a solid basis in science, and by definition is not irrational at all.