It is the last straw that breaks the camel's back.

A seemingly minor additional burden can trigger collapse when it comes after many earlier pressures. The final event is not necessarily the heaviest problem; it matters because accumulated strain has already reached its limit.

The saying highlights a breaking point rather than blaming one small act in isolation. It is used when patience, resources, or endurance have been gradually exhausted and one further demand finally makes continuation impossible.

Use it to describe a final annoyance, cost, demand, or setback that ends someone’s tolerance after a series of difficulties. It can explain an abrupt decision to quit, complain, or refuse further pressure, but may sound dismissive if it minimizes the earlier pressures that made the incident consequential.