Anne thinks everyone can be nble and good if they do one thing. What is it?

Here is the quote, (improve yourself)

"How noble and good everyone could be if, every evening before falling asleep, they were to recall to their minds the events of the while day and consider exactly what has been good and bad. Then, without realizing it you try to improve yourself at the start of each new day; of course, you achieve quite a lot in the course of time. Anyone can do this, it costs nothing and is certainly very helpful. Whoever doesn't know it must learn and find by experience that: "A quiet conscience mades one strong!”