Gawain and the Green Knight is a fascinating tale, full of esoteric lessons. A similar story is found in Irish mythology: This pre-dates the Gawain version and is, probably, the source from which Gawain and the Green Knight derives.
Apart from the Green Knight version, other variants exist ; notably, Sir Gawain and the Carl of Carlisle and Turk and Gawain.
It is also interesting to note that the original “Grail” story, from the Mabinogion, has a severed head on the platter as the main object in the procession. The importance of the head in Celtic mythology is to extant to venture into here, but mention of Bran (a Fisher King aspect) and his links to Arthur are worth mentioning.
Gawain’s importance among the Knights of the Round Table can not be ignored, he is the most significant despite efforts of later writers to denegrate him. Forget Galahad and Lancelot, for a moment, for these are to some extent late additions in the form that we receive them, and they gloss over the true importance of Gawain who is described by some later writers as a womaniser in some Christian variants of the Arthurian cycle. He is in fact a significant aspect of the feminine principle in spirituality, or more specifically the feminine principle within the male psyche. He also represents nature and I believe he represents the “natural state” of man, which is why he is of such importance.
In some respects I see The characters of Gawain and the Green Knight as aspects of the one psyche. They too, like Gawain and Arthur, can be seen in terms of Summer/Winter Kings and it is, obviously, a mythology concerned with the natural cycle of the yearly round, but what does the beheading aspect wish to relay to us?
I believe any beheading symbolism is teaching us the dangers of living “too much in the head” and neglecting the need to stay in touch with our body. Gawain is a representation of the Green Man (as is the Green Knight). As such, he is very much in touch with his natural state, his bodymind.
The challange issued by the Green Knight is – “Who is courageous enough to lose his reliance on his head/logical/rational/intellectual self and take note of his body/instinctual/natural self. It should be of no surprise that it is Gawain, alone, who steps forward.
For three days and three nights Gawain undergoes a test. Three days has a lunar significance; interesting when we think of Gawain as a solar hero. The moon is dark and unseen for three nights and is in its “hag” aspect.
Gawain is tempted and three times resists (well, almost!) – A reminder that we should not get too carried away and rely, solely, on instinct/bodymind either. We need to realise that we should listen to it, pay it our close attention, and integrate our headmind aspect to help it. Ultimately, it is about the balance between these two aspects of our conciousness. Those that succeed get to “keep their heads”
This is my interpretation and I guess each generation, each culture, maybe each individual reads and derives their own interpretation from tales such as these, but isn’t that the purpose and eternal gift of a true mythological teaching; that it does answer us when we ask the question? And it was Gawain who first asked that question.