由于快乐而忘记了忧愁to be so happy one's worries are forgotten

• 父母亲春天上阳明山赏樱花，两人也有乐以忘忧的时刻。

  Mother and father went to Yangmingshan in spring to admire the cherry blossoms. At times they were so happy that they forgot their worries.

• 我们去K歌吧，这样就能乐以忘忧了。

  Let's go to karaoke and sing our worries away.