It is important to consistently write our characters they way we designed them. This article is a good one on characterization.
Have you ever been reading a story when suddenly the protagonist does or says something that makes you think, “Oh come on! Why would he do that?” or “This is crazy. Why doesn’t she…?” or “But I thought he…!” or “I didn’t know he/she could [insert extraordinary ability].” The character seems to be acting illogically, to be making decisions with little motivation or contrary to his personality, abilities, or values. Learn more.