Redo
What good is undo without its trusty companion redo?
You can redo in Vim using <C-r> in normal mode — that is, hold control on your keyboard and hit r.
Redo is exactly what it says on the tin — it takes you in the opposite direction to undo, toward your more recent edits.
Give it another go in the editor. Write a few things, then undo the changes. Use <C-r> to walk back to where you were before.