My mother always says, 'but is an eraser word', as in, it erases what precedes it. This always comes to my mind when arguing with anyone and they say "but", but (!) the thought annoys me, because I think but is not always an eraser word, but inherently conjunctive is that even a word. And necessary. And now see where we are, with people using run ons instead.
I know that I sound like a loon 