In almost every episode of every reality show where contestants go up in front of a panel of judges – whether it's budding entrepreneurs on Shark Tank or wannabe singers on American Idol – there comes an uncomfortable moment.

A contestant has been rejected. The reasons are obvious to the panelists and obvious to the audience. Obvious to everyone, that is, except the contestant, who vows to continue chasing the dream. “This is my passion,” they'll often say, as if just having passion were enough.

It's not. Being successful is never just about passion. It's about being passionate about the right things at the right time. It's about using the head as well as the heart.

Speaking for myself, I can honestly say that I put my heart and soul into everything I do. When I say yes to something I do it with passion.

But I have also had to walk away from a number of ideas throughout my career because they simply weren't working. Sure, it can hurt, but you have to know when to say no, too. In any business – and in life – it is important to know when to be dispassionate, so that you don't let your emotions and desires cloud your better judgment.

It doesn't mean giving up; it just means evaluating your progress honestly, recognizing when a path you're on is not giving you the right return on your investment of energy, and, when necessary, re-directing your passion into something new.

By all means be passionate about what you do – there is no other way to live, in my opinion. But never let blind passion get you locked into the prison of one idea.