I guess as we get older we learn to deal with a certain level of insecurity in our lives. (phdinparenting.com)
Nonetheless, samples with higher levels of insecurity have shown the largest effect sizes. (child-encyclopedia.com)
As I mentioned before in this post on attachment, sometimes a person could have a mild or moderate level of insecurity, which is quite different from being extremely insecure. (scienceofrelationships.com)