What does "reality bite(s)" means. Is this phrase synonimous to "bitter truth".
Reality bites, the truth can be disagreeable and/or annoying.
We're told in kindergarten that we can be doctors, lawyers, poets, even fire fighters. The reality is, when we grow up we don't have the money to afford to go to medical school, the connections to get into law school, the creativity to be poet, or the height and weight to be a fire fighter. In the end we can't be whatever we want to be. Reality bites! The truth doesn't hurt, nor is it bitter. It bites - it's disagreeable and annoying.
Sensible, practical people with realistic ideas, on the other hand, are 'down to Earth' with 'their feet on the ground'; the opposite of floating in the air.
If the floaty people up there in the clouds ('in cloud cuckoo land') are forced to think about reality, the practical details, they fall from the clouds to earth. If it is sudden, shocking, and painful the do it with a bang - they hit the ground hard. A bang is to hit something hard, and/or the noise it makes.
"Cloud Nine" is understood,what is "cloud cuckoo land" ?
Cloud 9 is used when somebody has a reason for living a dream - they are in love, or their first book has been published.
Cloud cuckoo land is more negative. Cuckoo is a term used for crazy people, so cloud cuckoo land implies that they are dreaming because they are crazy.