Derpy often leads a clumsy lifestyle due to her constantly underestimating her bulky body. Her life really started to turn around however after she joined the Equestria police force. Due to her natural tendency to find herself in some of Equestria’s most catastrophic situations, she’s always manage to step up to the line of duty before anyone else even knows of the problem. Using her durable body, she is able to withstand any calamitous situation thrown at her and she has a 100% success/rescue rate, though her methods have been somewhat unorthodox as deemed by her peers.  
Nonetheless, no one would dare take her off the force, not only for her outstanding record and adoration by the community, but because most are afraid to ever get on her bad side.