When I am in a hypomania phase (I'm a BP II), I experience the following:
I take on WAY too much all at once. For instance, all of a sudden I'll decide that I want to learn how to crochet. Then I'll want to start practicing the piano again. And then I'll say that I am going to work out every morning at 6:00 am. Then I'll see someone playing the guitar and go... Wow - I'm going to take guitar lessons! Then I'll say that I am going buy a skateboard so I can do that. And then decide that I want to get back into yoga again. And start cooking all of my meals. And so on.
The problem is that I honestly, truly and wholly confidentally believe that I CAN do all of the things above - all at once. I have signed up for classes/activities for every single day/night of the week, and truly believe that I could handle it all. I will book my calendar solid without a second thought. What? Clean the house? Do laundry? Pay my bills? Uh... later... I have astrology class tonight. That's mania for me.
Usually the big sign for me that the mania is starting is that all of sudden, I'll get motivated to clean up the entire house. I might stay up late, until 1:00 am on a Tuesday just cleaning up and organizing the very house I neglected for the last three months while I was too depressed to do anything about it.
The other thing I'll do is I will be overly and excessively and perhaps inappropriately flirtatious with people. I'll do some from a judgement standpoint that I later regret, but it was something I couldn't seem to control at the time.
My thoughts are racing, I can't focus, think straight, I have too many ideas, thoughts or things in my head all at once. I can't focus on what other people are saying to me (I literally forget it as they say it). I barely can keep track of what in the world I am saying. I sound scattered, unfocused, etc.
I can tell it's mania because other people think I am insane/delusional to take on as much as I am doing all at once. They question how I am able to do so much. When you keep hearing that, you start wondering if you're doing something out of the ordinary. It's like I'm addicted to activity or distraction - whatever it may be.
And when you are manic, you start everything and finish absolutely nothing. If you're getting stuff done, you're probably just excited. With mania, I get massively distracted by the next interesting, shiny thing. I'll drop crocheting to go roller skating in a second.
Now with meds, I get excited about stuff and I'm able to get something done. I even finished crocheting a blankie!
I had my first pdoc appt when I was approaching a hypomania phase and I almost, almost cancelled it because I "didn't need her after all!". I felt so good, life felt so good that I knew it was all good from here on out. I forced myself to go, just because I promised my tdoc I would go to see if there really was a problem... And thank god I did.
Mania was literally the juice and soul of my life. It has you on a high that you don't ever want to get off of. It's like a drug. It wasn't a normal happiness or excitedness. I felt like Wonderwoman. When you are excited or have passion, you tend to follow through, passion is oftentimes linked with a commitment to the thing you have passion towards. Hypomania (for me) was about desperately trying to find something through any "shiny object" - there is no passion, just desperate and rapid searching through anything that might possibly "fulfill" you. Any one thing might give me a short term high, but it never lasts, so I move on to the next shiny thing as fast as I can.
I don't know if that helps at all... This is only my experience with it; yours may be very different.