That we can’t change our mind about a mark made in a painting simply by hitting an undo button teaches us persistence, tenacity, endurance, problem solving. “Keep going” is hardly the most inspiring of advice (especially in an era of quick fixes and instant gratification) but it is an artistic truth.
It also presents opportunities.
The fortuitous event, or happy accident, such as how the black ink has spread at the base of the jacket this model was wearing, suggesting shadow and adding a sense of movement.
Overworked, ‘mistakes’ in lower layers can become intriguing little details peeping through, and enrich colours.