push (one) over the edge

push (one) over the edge

1. To cause someone to commit to doing something they had been considering or close to doing for a while before. I tried to remain silent about my father's associations with the extremist group, but the events over the weekend have pushed me over the edge.
2. To cause someone to suffer a mental breakdown. Following on the heels of her recent divorce, the death of her father pushed Kate over the edge.
See also: edge, over, push