Great question. However, like joyful, happy, sad, etc there are so many to choose from. Painful? Most painful moment in 'my' life? I'll be truthful. Do not take offense to this reply since it has nothing to do with you, other than being a facilitator and your question is a writing prompt.
The most painful moment in my life to this point is answering this question. Not only did my focus go to my present physical ailments afflicting me at this moment, but those that are mental as well. Overwhelming.
Next, I drew upon my past life. Was a there a moment more painful than this moment reflecting on pain. What comes to mind is the book by C.S. Lewis titled "The Problem of Pain," Highly recommended read on this subject.
Now, I ponder the pain before me I anticipate experiencing - physical, emotional, mental, and social (I will go to work today).
And then, conflicted with experiencing the present pain of reflection, I seek pleasure to alleviate that pain. Some of those solutions may temporarily relieve the pain, but in the long run may cause further pain, i.e., smoke a cigarette, etc.
Now, a portion of a study I completed many years passed was the works of Francis A Schaeffer, which offers a solution too.
Finally the act which I will draw upon is mediation. I will listen to the sounds of the universe through natural VLF radio signals and meditate. Maybe the Universe will share something with me.
And, if you give credence to synchronicity your last name is the last name of the psychiatrist who's care I am in. Great Man! Second, I realize a good friend I have met here at hubpages is from the same homeland as Schaeffer. A connection? And, another finally, Lewis is my writing teacher of sorts along with the rest of the Inklings.
Now, I am not in pain - thank you, Malak!