"The definition of stupidity is doing the same thing over and over again and expecting different results."

It would be very difficult to chop down a tree with that mentality.

In quoting Einstein's definition of stupidity, the analogy is to ineffectively chopping at a tree without managing to fell it, and then proceeding to ineffectively do the same to N other trees.

First, the quote is about insanity, not stupidity. Second, Einstein didn't say it. Third, it's not a very good definition of either.