My boyfriend tends to notice when I'm becoming hypomanic a little before I do. He says that my behavior becomes very jittery, I become impatient, annoyed at small things, and sometimes he tells me my demeanor becomes very sexual even if it's unintentional (flirtatious, etc), and I start staying up a lot later. Those are the initial symptoms that I tend to not necessarily notice.

I do begin to notice by the time it's interfering with my sleep and I have a significant urge to get as many things done as possible.