First Principle Never To Let Ones

Marie Curie wrote this to her sister Bronya around 1899, during a period of intense scientific work and personal difficulty following years of financial hardship and the demands of raising a family while conducting research. The principle — never allowing external events to extinguish inner resolve — guided her through the death of her husband Pierre Curie in a road accident in 1906, after which she continued their shared research and took over his professorship at the Sorbonne.