The Cycle cannot be Broken

Sovereign informs Shepard of the cycle: organic species evolve, develop & create galaxy-spanning civilizations, and then the Reapers exterminate them. Sovereign also notes that its kind, not the Protheans, are the true creators of the Mass Relays & the Citadel. The Protheans were merely the previous of countless sequential civilizations who developed using Mass Relay Technology before being wiped out by the Reapers. And the time of the Reapers' return to begin the next cycle is near.

Example of:
Vicious Cycle