If anything can go wrong, it will. Murphy was an optimist. Anything that is to go wrong will do so at the worst possible moment.
Negative expectations yield negative results.
Positive expectations yield negative results. Every man has a scheme which will not work. Once you open a can of worms, the only way to re-can them is to use a larger can. The quantity which must be multiplied by, divided by, added to or subtracted from the answer you get to give the answer you should have got. An object will fall so as to do the most damage.