The reason why these people feel less satisfied is that a world of possibilities may also be a world of missed opportunities.   

请问:这里为何要用missed不用missing呢？是因为机会是被丢失的所以用被动吗？missing是不是可以看作形容词表示错失的呢，那为何不可以用missing呢？这里的missed是要看成过去分词做opportunities的前置定语还是可以直接看作形容词呢？