As the title implies, here we can discuss how characters can make mistakes that are stupid and sometimes fatal but also make sense from a story perspective. Like it doesn't come out of nowhere and fits the character's motives.
Two examples would be like in Dragon Ball Z where Vegeta fights semi-perfect Cell while Krillin attempts to shut down and destory Android #18. Cell convinces Vegeta to let him achieve his perfect form so "he can present a better challenge to Vegeta" as Saiyans live for the thrill of battle and Vegeta wants to defeat Cell at his best. Meanwhile, Krillin tries to shut down #18 but remembers her kiss to him and finds himself in love with her. These errors allow Cell to absorb 18 and give him his perfect form.