Where is the Undo Button when you need ?

I was working on a word document today and suddenly I noticed I had a tool bar missing.  I just hate it when that happens.  I really like the tool bars on my computer.  It is so easy to get things just right.  In fact I think we should have “Life Tool Bars”.  Copy and paste is good. If you have done something really well once then you don't have to risk messing up the next time.  Just copy and paste!  Now it is exactly the way it was the last time you got it right.  Insert is helpful too, did you forget something?  An appointment?  A birthday?  An anniversary?  No problem, just hit insert and if you forgot to do something there it is.  It got done in the right place at the right time.  But maybe the one we need most is the Undo button.  Did you hurt someone’s feelings, or do some embarrassing thing?  When you messed something up real bad there is that wonderful little button that just takes it away as though it never happened.  I used to have a boss that would say "Walker, you just missed another perfectly good opportunity to keep your mouth shut." Where is the undo button when you need it?