I tend to go with "No, thank you, I'm fine." It kind of re-frames their request as if they were offering to do me a favour, which I then politely indicated I d

I tend to go with "No, thank you, I'm fine." It kind of re-frames their request as if they were offering to do me a favour, which I then politely indicated I don't even need. I've found that it either cuts off most of the counter-arguments that the person asking was about to retort with, or it just throws them off-balance for long enough that the interaction moves on, enough that I don't get a lot of push back after using it.