PragProg - Programming by Coincidence

Ref: The Pragmatic Programmer

 Know what you are doing while you are doing it. Know why you are doing while you are doing it.

TIP 44: Don't Program by Coincidence

How to Program Deliberately

• Always be aware of what you are doing. Don't be frog in boiling water.
• Don't code blindfolded. Attempting to build an application you don't fully understand, or to use a technology you aren't familiar with, is an invitation to be misled by coincidences.
• Proceed from a plan, whether that plan is in your head, on the back of a cocktail napkin, or on a wall-sized printout from a CASE tool.
• Rely only on reliable things. Don't depend on accidents or assumptions. If you can't tell the difference in particular circumstances, assume the worst.
• Don't just test your code, but test your assumptions as well. Don't guess; actually try it. Write an assertion to test your assumptions.
• Don't be a slave to history. Don't let existing code dictate future code. All code can be replaced if it is no longer appropriate.

So next time something seems to work, but you don't know why, make sure it isn't just a coincidence.