Half the fun of editing images is in experimenting, and sometimes experiments don't turn out so well. As with most applications, Photoshop Elements includes an Undo function. I recommend you get mighty familiar with it. In fact, this is one place that it's a great idea to learn the keyboard shortcut.
To undo the last thing you did, choose Edit > Undo. Or press Ctrl+Z (Window) or Command+Z (Mac OS). You can continue to undo multiple actions.
The Undo History panel keeps track of your actions. You can go backward to any point in time, immediately undoing all the changes you've made since that moment; just click the point you want to return to. The actions you've undone are only dimmed—so if you want to restore them, just scroll down the Undo History panel to a more recent point.
Figure 4.7 Move back through time using the Undo History panel.
To open the Undo History panel, choose Window > Undo History.