Whether I'm walking, cycling or driving, I just assume that everyone on the road anywhere near me is very very VERY stupid and oblivious to the world around them, so I always assume the worst possible potential for an accident, and that way I'm never disappointed.
I always face traffic when either walking or cycling because I want to see the idiots coming my way BEFORE they have a chance to hit me, so I have time to react PLUS I want to have an escape route planned. I know that cyclists have the right-of-way and have the same priveleges on the road as an automobile, but I've seen enough idiots on the roads in autos to convince me that I will NEVER put my back to traffic. No matter what the lines on the road indicate, I will find a way to get from one place to another on a bike using the pavement, sidewalk, a grass easement, whatever, without putting myself in a situation where I'd have to trust that some idiot driving a car won't run me over from behind. Plenty of cyclists have died defending their right-of-way, and I don't plan on being among that statistic.
When driving I use my horn only when it's absolutely necessary; in emergencies or to prevent accidents, whether it's to prevent me being hit or to prevent someone from hitting someone else, etc. If someone cuts me off, I usually see it coming anyway because, again, I assume the worst, so I'm always ready, but I don't use the horn in that case, because the other driver already KNOWS that what they did was stupid - it may have even scared them when they realized that they've made a big mistake, so there's no point in me reminding them. In addition, to use a horn while surrounded by cars on a freeway may cause more trouble than it solves because some drivers are not confident behind the wheel and might not react well, or might over-react thinking that there's an emergency, and thus cause an accident. I'd hate to think that some woman and her kids got killed in a car crash because she panicked and swerved when I pounded on the horn because I felt there was no way I could let another driver cut me off and get away without me letting him know that I thought he was wrong.
An exception would be when I sound a quick short blip on the horn to alert a driver in line in front of me that the traffic light has changed while they were oblivious.
My reasoning for using the horn only whe absolutely necessary is that if we all used our horns to accentuate each syllable of our cursing, then, just like "The Boy Who Cried Wolf", the horn as emergency equipment might be ignored when it really counts, i.e., during a real emergency.
If everyone on the road was more considerate of one another and just set their alarm clock to wake them up a little earlier so they weren't always in a hurry, and then just backed off (I'm talking to YOU, tailgaters), chilled out, and listened to either Smooth Jazz or Classical music or comedy on the radio while driving, the world would be a much safer place. Unfortunately, there are those who think the world revolves around them, and they drive like Batman while drinking their Monster Energy drink because they're late for work and hung-over from last night's drinking, and they act like everyone's in their way and that it's everyone else's fault that their life sucks.
OK, sorry for the rant. This subject always gets me wound up. Stupid humans - I hate 'em.
It's no wonder that I prefer living out in the country, far away from them. It's probably just a matter of time before I crawl under a rock and write my manifesto...
Life! Life, do you hear me?! Give my creation LI-I-IFE!