Most arguments and disagreements stem from using the same word for multiple things. One of these words is "contradiction".
A person might contradict herself if she says something about a topic which doesn't apply to another one. For example, I can be a staunch defender of freedom of speech when it comes to my political faction, but I might take a more punitive position when the "freedom" to be defended belongs to my antagonist.
Another form of contradiction is the one that happens over time: I say something today that contradicts with something I used to say, or believe, in the past. There is a famous video out there showing the (many) instances when Steve Jobs contradicted himself. Or rather, his previous self.
The first type of contradiction is bad. At best it is a glitch. Normally, it is pure hypocrisy. The second one is not only excusable, it is recommended. I hope to be able to learn something as I move along in my life and there is no better way of showing that than contradicting with your previous self.
I will start using two different expressions going forward: parallel contradiction (bad) and sequential contradiction (good).