Lamentations 4:18 (ESV)

18 They dogged our steps so that we could not walk in our streets; our end drew near; our days were numbered, for our end had come.

During a siege, it was typical military strategy to build ramps against the walls of the city from outside. From these ramps, the enemy could shoot arrows and rocks into the city. That made the streets very dangerous to walk in. When this happened for more than a year, the people of Jerusalem realized that their end was near. The unthinkable was going to happen: the city was going to be taken in by the enemy.