Restraint is often mistaken for minimalism. They are not the same. Minimalism is a style; restraint is a decision about what deserves attention and what can quietly step aside.
Space is a material
Negative space gives the eye somewhere to rest and the subject somewhere to breathe. In a crowded frame, every element competes. In a restrained one, a single gesture — a hand, a shadow, the edge of a sleeve — can carry the whole image.
Light that does one thing
I prefer light that has one job. A single soft source can describe form, mood and time of day at once. Adding more light usually adds more information, not more feeling.
The goal is never to say less for its own sake. It is to make sure that what remains is exactly what matters, so the image holds attention long after the first glance.