I'm not perfect, but at the same time I try and make an effort with people, a smile, a wave, letting them out of a junction, carrying their bags / helping with a stroller, takes a minute or less out of my day, but hopefully it's passed on.
The way I see it, especially with driving is, if you can help make people less stressed and be a bit happier, they're less likely to drive aggressively, and therefore indirectly may help prevent an accident, or them hurting themselves or someone else. We're all responsible for one another on the road.
As I said previously, if someone is tailgating, rather than sticking the finger up, I'll try and let them pass me if it's safe, I don't know why they're in a rush, it could be an emergency, or it could be that they're driving like a dick. But so what? Me holding them up or getting aggressive with them accomplishes nothing, and gets me stressed too, or puts me at risk. Life's too short to prove a point