A travel mistake can stay small when it is handled before pride joins the conversation.

Wrong train, wrong turn, wrong booking are all cheap in the first few minutes and expensive once somebody starts defending themselves. The energy goes into who is at fault, the mistake keeps running while the argument happens, and a fixable thing becomes the story of the day. Speed matters more than blame when you are away from home.

Say it out loud as soon as you notice, with no preamble about how it happened. Fix first and discuss later, if at all. Whoever made the error will feel it enough without any help.