Almost everyone hurts when someone you love and care so much about doesn’t respond. But if not getting a response disrupts your life so much that you can’t function normally, it’s not about that text your ex didn’t respond to, or that they didn’t call back, it’s about much deeper unresolved issues going on inside of you.
In order to be successful in this process you need to learn to separate what thoughts and emotions are about what’s really going on, and what thoughts and emotions are a result of your anxiety, depression, fear of rejection, tendency to overthink and/or overreact, rush to negative conclusions, neediness, control issues, etc.