1. Nothing is as easy as it looks.Other Authors and Sources
2. Everything takes longer than you think.
3. If there is possibility of several things going wrong, the one that will cause the most damage will be the one to go wrong.
Murphy’s Law: Colrollaries
In Arthur Bloch, Murphy's Law: And Other Reasons Why Things Go gnorW, "Murphyology" (1979). See Murphy's Law.