One of my college Physics professors said something one day that stuck with me. Someone in the class said 'back and forth' and he stopped them and said that it was physically impossible to go back and forth. You can go forth then come back to the initial state, but you can't go back then forth. It was a very literal interpretation, but it stuck with me all these (many) years.
I made the mistake of using that on my boss a while back and he's not let me forget it yet. Of course, he reminded me, you can go back then forth if you're talking numerically - start at zero then go back to -3 then forth to 6. I agreed, but I'm sure he'll find other examples and ply me with them.
He mentioned a good one and I promised to write about it. He said - think about all of those products that are new and improved. Think about it, they can't be both new AND improved. That have to be one or the other.