Experience is what enables us to make a new mistake each time. The man who smiles when things go wrong has thought of someone he can blame it on. The Thinking Rule. A badly thought out project takes three times the expected time, a well thought out project only takes twice the expected time. Wood's Third Law.
Every action has an equal and opposite ulterior motive.
Newman's First Law. Every body will remain at rest until the boss gets mad. Anthony's Law Of Force. Don't force it get a bigger hammer. Never trust a computer bigger than you can lift.