I was climbing the other day and in exhaustion said “lord” but realizing this said “have mercy” quickly after. Would I be in a state of mortal sin?
If you’re unsure, it’s best to ask your Priest.
You’ve asked this question before. Saying “Lord” in the situation you’ve described is technically a prayer and therefore not using the Lord’s name in vain. The only way to use the Lord’s name in a sinful way is when you substitute it for/ use it as a curse word.
This may help you answer your question.