How to be a Christian without being exploited?

Being street-smart used to be my second nature; I grew up in a rough neighborhood and learned at an early age that people take advantage of others. After all, I have been through as a loyal, though imperfect Christian, I have to ask, how do peaceful Christians or those of any faith really live their lives without being taken advantage of? How do we find our inner lion again instead of our inner deer? Sometimes I need to be able to fight back without feeling remorse.