Notebook fills screen and resize arrows are not visible

The following notebook fills my monitor screen. Resize arrows on margins don’t appear, and MMA taskbar has disappeared. So, I can find no way to resize the notebook so I can minimize or shut down. When I restart the computer, the MMA notebook again fills the screen and I can do nothing but run MMA. How do I exit this mode?

I opened the notebook in a text editor, and found the option WindowSize->{Full, Full} near the end. If I remove it, then the window size becomes normal. Anyway, on my mac I can resize it by dragging the pointer to the top of the screen, so that the window header shows up.

Thank you, Gianluca. I’ll try that.

Gianluca pinpointed the cause of the problem. To fix it add the cell below to the nb, and evalute it:

SetOptions[EvaluationNotebook[], WindowSize -> Automatic]

Thank you, Hans. That worked beautifully. I think I must be pressing buttons in error for such things to happen seemingly at random.