That's the actor-observer bias, in which people tend to see their own actions as episodic and necessitated by external factors, while seeing the same acts by others as consistent character traits. To wit:
I like to take a few minutes to unwind on the couch. You are lazy.
I have an occassional sweet to round out a nice meal. You need to watch what you eat.
What about the positive-negative bias? It seems like a similar attribution error:
I suck. Occassionally, something manages to go right.
People don't really like me. Sure, I was invited, but only because he invited everyone else in the crew.