Einstein, like all big brains was confident perhaps to the point of arrogance (at times). However, he was also humble enough to admit he was wrong and did that when he was proven wrong.
When Einstein submitted a paper arguing that gravitational waves don't exist to Physical Review, the journal’s editor sent it back to for revisions. Outraged, Einstein withdrew it. By the time he submitted it to another journal, he had corrected his mistake. The revised paper argued that gravitational waves do, in fact, exist.
Almost every "great" physicist and engineer I have worked with will argue to the death that they are right. When you are in their field, they are not humble. However, what separates them from the not great ones is while they are arguing to the death, there is a little voice in their head going "maybe I am wrong". Arguing to the death is part of their process, even if unconsciously, for testing and refining their ideas. The not great ones don't have that voice. Their arguments become emotional, perhaps personal, and they won't go back and look for errors and test their hypothesis, but will look for reasons they are right. Even when it becomes obvious, even to them, that they are wrong, they look for ways to make it seem like something extraneous was responsible for their failing.
