I'm a disbeliever. I tend not to believe people's claims about what they think is the truth. I am Skepticism Incarnated. After eating and sleeping, disagreeing comes third on the list of basic necessities in my life.
It's because I like thinking. I'm quite sure that I have some weird physical disability that makes my brain inject endorphin in my blood whenever I'm thinking. I think all the time. It's as if I'm on drugs from the moment I wake up until the moment I go to sleep. People often find me staring into nothing for minutes, ignoring anything that happens around me. I'm usually the last one to notice that the office is on fire.
Disagreeing with people forces me to think. It makes me want to find other solutions to the problems they think they solved. Out-of-the-box thinking is second nature to me, since I have to go all the way around a problem for a lucky chance to invalidate someone else's claims. This leads to daily disagreements, like these...
"My work is finished!" - "No it isn't. Look at this part, it doesn't work."
"The customer absolutely needs it on July 31!" - "No they don't, they only think they do."
"These features are all required." - "I'm sure they are not. Let's delete some of them."
"Project managers should lead the teams." - "Over my dead body."
"We need better processes." - "No we don't. We need better people."
"My collegue did a bad job." - "I'm quite sure you could have prevented that."
I think a healthy level of daily disagreements is essential for any manager. It forces you to think and come up with solutions other people never thought of, because they are lazy thinkers.
Don't believe the management books you're reading. Don't believe a production pipeline is bad for your development team. Don't believe that cross-functional teams are better. Don't believe that MoSCoW priorities help customers in selecting requirements. Don't believe the world is getting warmer. Don't believe that Char is a spiritual medium. And most important of all: don't believe me!