The matter of sometimes being nervous with customers at work might fit in a slightly different category of some kind, but I think the others above are related to our feeling or at least wanting to feel "protected by the herd" or experiencing "the protection of human community". Like you, I could easily become anxious at the thought of not having my own "inner circle" of friends for security in a sometimes-hostile world, and maybe something as simple as "Count your blessings" while including them at bedtime could help alleviate the nightmares.