My interpretation of that line is that: Whether you encounter triumph or disaster is too often determined by factors outside your control. There will be times

My interpretation of that line is that: Whether you encounter triumph or disaster is too often determined by factors outside your control. There will be times in your life when you try your hardest but still fail. And, other times, you will succeed despite your worst effort. And so, triumph and disaster are imposters insofar that they are inaccurate reflections of the things that truly matter -- persistence, hard work, integrity, etc.