【忘其所以】〖wàng qí su y〗[forget oneself; become delirious with joy; forget everything in one's joy; get a swelled head; forget]

忘寝废食著诗典，

其命维新汉英翻。

所欲从心世界语，

以诚相见大同寰。

因过分兴奋或得意而忘了应有的举止。Because forget what due due with excessive excitement or pride. 同：忘乎所以、得意忘形。反：谦虚谨慎。