"Habit is a second nature that destroys the first. But what is nature? Why is habit not natural? I am very much afraid that nature itself is only a first habit, just as habit is a second nature"

Blaise Pascal is recommending that habit can be so powerful that it can override our all-natural instincts. He is doubting what is thought about to be natural, and suggests that nature itself is just a practice that we have come to be accustomed to. He is suggesting that our behaviors can come to be so deep-rooted that they can become our acquired behavior, as well as can even override our first nature. This suggests that our habits can be so effective that they can shape our lives and also our actions. He is advising us that our behaviors can be so solid that they can bypass our natural instincts, and that we need to be aware of this. He is suggesting that we should be mindful of our behaviors as well as how they can form our lives, and that we must take care not to allow our behaviors become our force of habit.