Going to my workplace, I usually place file-folders in my bag (see figure 1).
However, after some time of using this file-folder, the top and top-right are both curled into the middle (see figure 2), between the front and back sheets of the file-folder.
How can I straighten the top and top-right so that it no longer curls inward?
How can I prevent new file-folders from curling inward when placed in my bag?
I have tried flattening it with my hands and placing it under a heavy object for a few days. This lessens the curls, but eventually returns to the curled-in state after placing it in my bag again.