Definitely the fourth precept. Lying isn't really the issue, it's more a matter of swearing and getting irritated with some people, hence the tone in my voice isn't the lightest. Maybe my issue is more a matter of Right Speech, but I figured this would mean the fourth precept is the most difficult for me. The others aren't really an issue. I mean, I'm sure I accidentally kill insects, but it's never intentional. I've noticed that sometimes I'm about to step on an insect unawares, and I look down, and purposefully move my foot or stop it or something so that I don't kill the innocent insect. I maybe look at eye candy too much, however. Irregardless, I can somewhat control that if I become more aware of what I'm looking at.