"Always code as if the guy who ends up maintaining your code
will be a violent psychopath who knows where you live."
- John Woods, 1991
(note that this quote gets attirbuted to a lot of people and I'm only like 5% sure John Woods was the original speaker)
Not mine, but there's a few people I wish I could beat this into...
As for my own:
"You should never delete/delete what you new/new
because you should be using smart pointers anyway.
And if you can validly disagree with me, I'm not talking to you."
- Cornstalks, 2013