Firefox assumes that if the browser crashed, you probably want to restore your previous session. This can happen automatically, but because of infinite loops of crash and restore, the "This is embarrasing screen" was created to let you just start a new session.

What would you prefer: just restore, or just start a new session? Do you ever want to use session restore?

Make sure that Firefox closes properly.

Try to use "Firefox/File > Exit" (Mac: "Firefox > Quit"; Linux: "File > Quit") to close Firefox if you are currently doing that by clicking the close X on the title bar.

See also:

• "Hang at exit": http://kb.mozillazine.org/Firefox_hangs
• "Firefox hangs when you quit it": https://support.mozilla.org/kb/Firefox+hangs