Idioms - part 3

Once in a blue moon

1) He cleans his room once in a blue moon.

it means

He cleans his room very rarely.

2)  You don't have to worry! our CEO comes here once in a blue moon and he never checks anything.

it means

You don't have to worry! Our CEO seldom comes here and he never checks anything. 
                                                                                                CHECK 

To take the bull by the horns

1) If the group is noisy, the trainer must  take the bull by the horns.

it means

If the group is noisy the trainer has to control group behaviour.

2) It's time to take the bull by the horns and get this job done.

it means

We mustn’t pay attention to difficulties, we have to complete this task.

                                                                                                 CHECK