Verb (5-dan, る, intransitive)
1. to soar; to fly high; to be whirled up
そして、上空へと舞い上がっていた。And, it was soaring up into the sky.
2. to make merry; to be ecstatic; to be in high spirits
もしかしたら僕が勝手に舞い上がってるだけなのかも。Maybe I'm just getting carried away on my own.