Walking on air
«Andar por las nubes»
This idiom, which is similar to be on cloud nine, means to be extremely happy, delighted or joyful.
This idiom, which was coined in the XX century, is usually related with feelings of extreme happiness. On the other hand, we generally associate the ground, with being realistic, like when we say put your feet on the ground or get back to Earth. We also associate the ground level with being depressed. If a person feels sad, we say that this person is down. Conversely, when a person is extremely happy, cheerful, optimistic. if the person is dreaming with open eyes, we can then say that this person is walking on air.
María gave her first love kiss yesterday. Now, she is walking on air.