I was recently asked what the most difficult thing I have ever done was, and the answer is simple: being a father. Nothing I've ever done in my life compares to being a father. Because nothing else really mattered. If the product I want to develop, the disease I want to cure, or the deal I want to do doesn't work out, there will be a thousand more things to attempt the next day, but I only have one chance, one moment with my children, to do the right thing.