Does karma truly exist, or is everything just circumstance and luck?

I have tried hard to live a life of values, without lying one bit and trying to be truthful, but I have found that this does not seem to really matter because even if you tell the truth, people are still bound to tell you you’re a liar.

I have found people that have done horrible things, and live wonderful lives. How does this work? Does karma exist? Does it even matter if we try to live moral lives?