In any field of scientific endeavor, anything that can go wrong, will. If the possibility exists of several things going wrong, the one that will go wrong is the one that will do the most damage. If nothing can go wrong, something will. Left to themselves, things always go from bad to worse.
Nature always sides with the hidden flaw.
Given the most inappropriate time for something to go wrong, that's when it will occur. Mother nature is a bitch. If everything seems to be going well, you have obviously overlooked something. Never make anything simple and efficient when a way can be found to make it complex and wonderful. If it doesn't fit, use a bigger hammer.