a cloud on one's happiness的用法和样例：
- The bad news cast a cloud on them.
- There is a cloud on the horizon that may overshadow the talks.
- To define wind speed and direction look at the shadow of a cloud on the ground.
- I am sorry to cast a cloud on the party, but I am afraid there's been some bad news.
- People had to run for cover as thousands of the tiny insect swarmed like a cloud on fields in Cromer.
- A cloud is a mass of vapor in the sky.