Other whites also tend to, largely subconsciously, hold your behavior to a higher standard of conduct than they would a person of minority descent, and be quite a bit more punitive in judging what they determine to be a failure to meet those standards.
I work retail, for instance. We've got black employees here who routinely show up 10 to 15 minutes late for work, suck at customer service, and randomly disappear for thirty minutes at a time or more during their shifts to fiddle around with their cell phones. Yet... No one ever says anything, nor do they lose their jobs.
Me, on the other hand? I can't even take a dump on the job without having some grouchy manager give me a hard time over it.
Hell! I got caught glancing at my cell phone to check my messages one time, and it was brought up in every performance review I had for the next 6 months!