If your startup needs multiple miracles to succeed, you need to go back to the drawing board and come up with an idea or product that has only one miracle. Otherwise you are multiplying out multiple low probability events and are extremely likely to fail.
Many people delude themselves on whether they are a one-miracle, or multi-miracle startup. They way to tell is to ask yourself what your product or business end goal is. Is your approach directly focused on achieving that end goal? If not, you may have a multi-miracle plan without realizing it.
Yep. Although I disagree with Elad's assertion that:
If your startup needs zero miracles to work, it probably isn't a defensible startup.
That is true only in a winner-takes-all market. Some markets are naturally fragmented. You don't need a miracle to build a successful web development company, you just need competence, hard work, skill, luck, good business relationships, and a dozen other tricky but achievable ingredients. And, depending on your definition, those can be startups too.