Whatever can go wrong, will go wrong (and at the worst possible time).
Murphy's Law is sometimes also presented as a life philosophy. Also embodying defensive design, many simply see it as a way of saying in the approach of anything whatsoever that could have a possible flaw (be it an engineering project, a romantic relationship, an argumentative case, carrying an upright bass down a flight of stairs, or putting on your suit), then it's always within good measure to make the necessary precautions to make sure that those flaws can't happen. Many see it as the initial meaning behind what Murphy was saying, a simple philosophy of defensive design that has been highly misinterpreted. However, this is left open to controversy.Read more on Wiki