answer:When using Photoshop, you should always clone and lock your layers. Clone and lock your first layer and then each layer after you save. Turn them invisible so you can see the current layer you are working on. Also when you begin a project, make sure your history is set to show the last 50–100 edits done so you can easily go back if you don’t like a change you’ve made. If you don’t clone your layers or have your history set to 50 or more, I’m sorry but your changes might be permanent. =[ It took a while for me to get used to it. You can’t just click undo because it will only undo your last edit.