| Clue | Source | Date |
|---|---|---|
| Come up against difficulties that can't be overcome | ||
| Couldn't go on | ||
| Reach the limit | LA Times Daily | 17 Jun 2017 |
| Reach the limit | The Washington Post | 17 Jun 2017 |
| Reach the limit | ||
| Be unable to make further progress | New York Times | 22 Nov 2015 |
| Be unable to make further progress | ||
| Stop suddenly |