On theory

“It doesn’t matter how beautiful your theory is, it doesn’t matter how smart you are. If it doesn’t agree with experiment, it’s wrong.” – Richard P. Feynman

Optimisation

Don’t be too quick to optimize code for computers, human beings experience pain, computers don’t.

Solving the right problem

“No matter how good the team or how efficient the methodology, if we’re not solving the right problem, the project fails.” –- Woody Williams.