When riding in traffic I move out the mirror ever so slightly, so I can see if a car is going to drive really close to me, trying to cut you off. I'm sure I've had a few people intentionally try to squeeze me off the road.
This style of mirror was perfect for me, just hangs out far enough I can see around my larger sized body. I don't need one on my right. The left does all the work. And besides I don't want to look to much like a motor bike... ESH!
- Don't just worry about your own driving, be aware of everyone elses driving too.