Why is a destiny achieved by the decisions you have made preferable to a destiny that comes from chance or luck?
This is, of course, a matter of opinion. However, you can argue that the "destiny" that you acheive on your own is better because it is more fulfilling and rewarding.
Think about the feeling that comes along with making money. A person who makes a fortune based on their own decisions and efforts can feel proud of themselves. They can know that it was their hard work and/or their wise decisions that made them succeed. By contrast, a person who wins the lottery merely feels lucky. They know that they did not do anything to earn or to deserve the money. It is a much less satisfying feeling because they know that this destiny came to them just by luck and not through any effort of their own.