turning point race against time pinch pivotal moment critical moment Critical Periods shift turn of the tide Cross-road crucial moment high noon pass crunch cross-roads crossing crisis Critical Period development moment of truth decisive moment climax defining moment hinge axis zero hour twist culmination juncture critical point nexus critical moments critical mass transition turn the tide cusp climacteric crucial period change peripeteia pivot emergency crux when push comes to shove contingency point of no return crucial occurrence exigency strait peak kairotic moment crossroads