Photoshop: the next level

[Mylqin]

Good Photoshop Habit:

Have you ever flattened an image and then was betrayed by ctrl+s? Downsized a file just to have it overwritten while you haven't been paying attention?

Here is a solution to your problems!

I have created the habit of never using the flatten or resize down command before duplicating my image. It's as simple as

Image > Duplicate

This will create a new file where, if you accidently press ctrl+S, will prompt you where to save the new file. It works both ways - if you save your original file flattened by accident, you still have a copy with all layers and resolution intact.
Remember to duplicate before flattening! Saved me more times than I could count.

There's also the History tool snapshot feature which lets you save the version your previous version and you can recover it at anytime during the work session, although I prefer your method of creating a new image (which I just save as when scaling or flattening) this can help in a number of ways as well.