Feeling insecure is an extremely common emotion that everyone experiences at some point in their life. Many of us feel as though we are not good enough, we do not measure up to others, we cannot do anything right. I’m not sure how your insecurity manifests itself, but it can cause us to distance ourselves from others. If you are having feelings of insecurity then these are fueled by your thoughts, by the internal dialogue that you have with yourself all day long.
It helps to identify the negative thoughts you are having about yourself and how those thoughts are effecting your relationships and causing you to feel as though others will abandon you. Also, challenge and replace those thoughts with the truth about yourself. I do not know if you are a Christian, but I know in my own life, when I have experienced times of insecurities about myself I read and memorize different Bible texts that show me who I am according to our Creator, Jesus. This always help me put my thoughts in order and find my security in Him.
Insecurities are likely to always pop up, but if you learn to take control of your thoughts I believe you will find that you are more secure in yourself and your relationships.