I agree with ElsaMars... I'm not sure about hypomania. Sounds like normal happiness.

Stimulants are known to cause euphoria when you first take them, but that euphoria usually isn't like a bipolar hypomania euphoria. It's more like what you described-- happiness, motivation, etc

I actually became agitated and paranoid when I took Adderall for the first time. It was a nasty dysphoria. It started off with normal happiness like you got, but quickly (i.e., within 12 hours) made a turn for the worst. (Probably because I was taking Adderall XR as opposed to Adderall IR. IR wears off after 4-6 hrs, but XR keeps going!!!)