My work in Photoshop is hampered by the following obsessive suspicion. Please either bust or confirm the myth.

I believe:
Resizing a rasterized layer multiple times in a PSD will destroy its image quality.

Is it true that upon each use of the Free Transform tool, information is interpolated and/or discarded, such that multiple applications will hurt quality? I believe this and attempt to resize raster images to their destination size only once, at great time expense.

Or does the PSD somehow retain the full information of the original image, simply recalculating its new size upon each application of the Free Transform tool (or other resizer)? If that's true, my obsession would be lifted and I could work at a reasonable pace.

What do you think? Myth or fact?