Insecurity is a feeling of general unease or nervousness that may be triggered by perceiving oneself to be unloved, inadequate or worthless (whether in a rational or an irrational manner).

A person who is insecure lacks confidence in their own value and capability, trust in themselves or others, or has fears that a present positive state is temporary and will let them down and cause them loss or distress by "going wrong" in the future.

-Wikipedia