Don't believe the lie. You know the one echoing inside your head, taunting you and whispering, "You're not good enough or smart enough". It says, " Because of your past you're not lovable". It encourages you to compare yourself to others so that you will think you're not beautiful, should be further along in life, and will always be alone.
Insecurities - we all have them. They are birthed out of a feelings of inferiority. For one reason or another we've bought a lie that some aspect of our self isn't good enough, causing us to think less of ourselves.
At times I'm very insecure about my shyness. I'm a bubbly, silly, always laughing way-too-much kind of girl, but that's not a side of my personality many people see.