But who can say what's best? That's why you need to grab whatever chance you have of happiness where you find it, and not worry about other people too much. My experience tells me that we get no more than two or three such chances in a life time, and if we let them go, we regret it for the rest of our lives.

This quote is suggesting that you should grasp any opportunity for happiness that you find, and not stress too much about what other people think. The speaker is drawing on their own experience, and they believe that we as humans only have two or three chances of finding happiness during our lives. If we do not take advantage of those opportunities, we will regret it in the long run.