I will preface this with I am a mental health provider. I have been living with Dysthymia (low level persistent mood disorder) for about five and a half years. It is easily masked and no one outside of my wife, a close friend and my therapist even notice it.
I go through the motions of everyday life and my existence is empty. I rarely feel excited for anything. For example I am seeing band on my concert bucket list this weekend and it feels no different than going to work everyday. I am chronically exhausted dispite a fairly consistent sleep schedule. I also do not sleep without a sleep aid. I am a non-smoker, rarely drink alcohol, exercise regularly and have an active social life (that often feels like a chore).
In my case Dysthymia was brought on by a traumatic head injury at work. Since my career has felt like a plateau though I continue to move forward. It just is empty and monotonous. I see no real future.
If anyone else is experiencing this, feel free to reach out and know that you are not alone.