Have you just observed your "mood" without any desire that it should be one way or another, good or bad? You know it cannot last very long. Different chemicals are released in the body and we label these things with words like sad, afraid, anxious, good mood, bad mood. None of it is permanent, though. It is an ever moving stream.
The "mood" has long passed, yet you are still thinking of it. I wonder about this.
The main challenge i see is this one word u r using: Thinking. When thinking subsides the mood passes and u r feeling good again. U r free of the mood. Meditation relinquishes such thoughts. However we must also recognize that Rome was not conquered in a day and very few of us conquer ourselves in even a life time. It is good to have patience with ourselves and recognize what we still need work on while recognizing the small accomplishments we have made. Yes i also wonder. Why r some thoughts and moods so persistent and often return?
"The "mood" has long passed, yet you are still thinking of it. I wonder about this."