The tip of the iceberg
a small visible part of a much larger problem
At the end of your rope
having no more patience or strength to deal with something
Count your chickens
to plan for something that has not happened yet (usually a warning)
Bite off more than you can chew
to take on more than you can handle
Examples
These complaints are just the tip of the iceberg.
After three sleepless nights, she was at the end of her rope.