You blame their character. You blame your own bad day.

When someone else cuts you off in traffic, it's easy to assume they're simply reckless. When you do the same thing, you point to the emergency you're rushing to. Social psychologists call this bias in explaining others' behavior by their character while explaining our own by circumstance the fundamental attribution error, first named by Lee Ross in 1977.

— Lee Ross, The Intuitive Psychologist and His Shortcomings — Advances in Experimental Social Psychology, 1977