toreachapointwhen you arerunning,exercising,playingsports, etc. where you are sophysicallytiredyoufeelyou cannotcontinue:
Manymarathonrunnershitthewallat around 20miles.
In thefinal, with astrainedhamstring, Ihitthewall.
Everylong-distancerunnerhitsawallat somestage.