The key to changing a habit is to invest heavily in the early stages of habit-formation so that the behavior becomes automated and we later default into it rather than exhausting our willpower wrestling with it. (From "how to make your own luck", brain pickings) Hi, I am having a difficult time to apply the definition of "default" in this context above. Default means "to fail to perform sth" according to dictionaries, yet the definition doesn't seem to fit in to this context at all. Could you help me to understand this sentence? Thanks!