"A life of leisure and a life of laziness are two things. There will be sleeping enough in the grave." -Benjamin Franklin
This philosophy is slightly flawed, in that you actually need sleep in order to take advantage of opportunity. I can say what it is like living by this philosophy; you can get pretty tired sometimes (or most of the time). I manage to enroll myself in every opportunity that crosses my path: Physics Club, Student Ambassadors, Boy Scouts, Karate, school (which is actually required), robotics. I do think that doing many things is good for you. It gives you experiences that you wouldn't get otherwise, and makes you, a) happier, and b) a well-rounded person. I strongly recommend taking advantage of opportunities; you will be busier, but you can get used to it. The problem with this quote that I can see is that it encourages you to overdo it. Take my advice: don't.