Unhappy people with an inner voice have a grumpy crank personality as their inner voice. Taming and neutralizing that grumpy crank is the entire point of the Cognitive Behavioral Therapy school of Psychology. They have a process called an Inner Dialogue Audit where a list of 10-20 simple questions are given, and you ask yourself these questions. If you answer "yes" to any of them, then your inner voice has a bias, is effectively lying to you about your moment to moment observations and thoughts. And once this bias is identified, it evaporates because deception known no longer deceives.