the straw that broke the camels back

The straw that broke the camels back is typically the last in a series of unpleasant events that make someone feel they cannot continue to accept this bad situation. It usually is said after a long string of bad things happening, typically done intentionally by somebody or other types of unpleasant situations. The straw that broke the camels back is usually the one (possibly light or meaningless) thing that pushed someone over the edge.