To me, that seems to be the hallmark difference between hypomania and "real" mania, and what makes the latter more dangerous and scary-- the loss of insight into the condition, or that there even is anything amiss.
It hasn't reoccurred, but i'm now very aware that what I experience as reality is completely subjective to how my brain is functioning. Anything I experience right now could be a different version of reality. But at the same time, now that i'm aware it has happened, I can keep that in mind and consider it in the future. I have to believe that different forms of mental illness allow for the same kind of self-awareness, but it depends entirely on what parts of their brain are functioning (like if they can control their emotions and think clearly, which is hard enough for "sane" individuals already)
This is a big part of why schizophrenia is so hard to treat. With other disorders like OCD, patients generally do know they are unwell and are willing to accept treatment to improve it. With schizophrenia, patients are often rigidly convinced they are already healthy and refuse to be treated. They are incapable of understanding that they have an illness.
There's a big difference between the three. The first, the ones who know and care about it - you probably won't even notice he/she is suffering from it, unless they tell you. The others.. yeah.
Source: used to be a med student and a trained hospital sitter.