I was told by a psychologist that people with bipolar disorder can experience a lot of "mood lability". "Mood lability" as she defined it are periods when the mood seems elevated a little (or the opposite), but the full criteria for an episode is not met. Certainly if you just feel up for part of a day and then you're fine, that is not a diagnosable episode. Hypomanic episodes must consist of at least 3 symptoms in the DWS-5 list (if elated) or 4 symptoms (if mostly irritable) and last at least 4 days, with symptoms most or all of the day.

It would be a good idea to ask your psychiatrist about this mood lability to see if it's within a normal range of...normal excitement. Or, something else.