Know your skill level. Ron rides more aggressively than Donna, but that's because he can ride at traffic speed. I take up a whole lane now. Some drivers get upset, some wait and pass safely. He considers himself a skilled, experienced rider with traffic savvy who's lost his edge due to sheer numbers.
Traffic volumes are so much more now.
More volume, higher incidence of people being careless or rude or not seeing you. Develop a network of friends for emergencies. If you ride with a carpool on some days, ask if the driver will provide an ride should an emergency arise. Know your transportation options. Keep current a bus, train or ferry schedule with you or in your desk, along with fare.