Dreaming of a beheading means realizing that you have made a mistake that is detrimental. You may be able to hide the mistake now, but heads will roll once it is uncovered. Realizing this, it will cause a lot of harm and stress to your overall well-being. Your brain is trying its best to play out scenarios of the detrimental mistake, and ended up with a beheading sequence. Seriously look for an exit plan as this is not something to try finagling out of.