exuberance
the quality of being full of energy, excitement, and cheerfulness
Link to present incidents:
The Observer today quotes Reiner Klingholz, director of The Berlin Institute for Population and Development: “There is no example of merging two states with such vastly different political systems that has worked so smoothly. But this reunification was, and continues to be, far more difficult to achieve than was thought during the exuberance of the reunification celebrations.“