In a couple chapters of his book, Jacobs works on gossiping. According to the book, the Bible has at least 20 passages condemning gossiping. And, I don't think that means eliminating talking badly about other people, but talking about people behind their backs at all, really. But, what happens when your significant other comes home after a hard day and vents to you about his or her coworker (as did Jacobs' wife)? Instead of offering moral support with a "you're right, what a freakin' jerk," you sit there and listen silently and then say, "ah, that's too bad." As with the author's wife, that may not go over too well.
In the same vein, Jacobs writes that really, it's better to not talk negatively at all. Jacobs admits he fails on a daily (hourly) basis. I mean, think about it: how many conversations do you come across every day that are negative in some respect? How many are you a part of yourself? Me? A LOT. People bitch and complain - that's what we do. But, after reading about how hard he's trying not to speak that way, maybe the world would be a brighter place if we all cut back on it a little.
When he comes back to the topic of gossip several chapters later (Do not go around as a gossiper among your people... Leviticus 19:16), Jacobs mentions that the more he keeps his negative thoughts to himself, the fewer negative thoughts he thinks up in the first place. "I refuse to let that toxic cloud gather in my brain. It's a purifying feeling..."
Couldn't hurt, right?