“Thrift is merely common sense in every-day working action.”
The principle is made practical rather than glamorous: ordinary, repeated decisions about work and spending matter more than occasional dramatic gestures.
Source details
Thrift, Chapter II, “Habits of Thrift,” Project Gutenberg #14418. Smiles says thrift requires neither exceptional courage nor intellect but ordinary common sense, resistance to selfish enjoyment and patient self-denial.