Sometimes hypomania feels like being high to me. Music sounds better, perception is altered, thoughts are scattered, I'm a bit forgetful, etc.
If you're high and don't want people to know, a good trick is to not talk much. If you don't say anything, you might not be found out. Sometimes when people get high they tend to talk a lot, and talk fast.
A classic symptom of mania or hypomania is pressured speech, or rapid speech. When I'm hypomanic, I feel like my thoughts are flying fast, and it's hard to keep up. Fortunately for me, my thoughts still make sense when I'm hypomanic.
If I know I'm hypomanic, I'll usually try to act normal. One of my tricks is to remember not to talk too much. This not only helps hide a symptom, but it also makes it less likely you'll say something you'll regret. It also helps me to control myself.
I'm not suggesting that you hide your symptoms, but for me, I'm just going to have them sometimes. And I often want to function normally.
(Side Note: I've listened to someone talk while completely manic, and it was way beyond just fast speech. Their thoughts jumped from one idea to the next and they didn't make much sense. They needed help.)