How to express psychological insecurity (not physical insecurity)?
Security (think: Otis Redding) is 安全感, a very popular and common concept in Chinese.

——

Oxford gives the example:


  有安全感
  have a sense of security


——

Insecure is 没有安全感.

Oxford has the example sentence:


  她没有安全感。
  She feels insecure. 


I think Cantonese would opt for 缺乏 over 没有 giving you something like:


  缺乏安全感