1. a state of intense happiness and self-confidence:
She was flooded with euphoria as she went to the podium to receive her Student Research Award.
2. Psychology. a feeling of happiness, confidence, or well-being sometimes exaggerated in pathological states as mania.
The people most familiar with euphoria are pilots of high flying aeroplanes because an insufficient supply of oxygen at altitude can and will bring about hypoxia (where the body at the tissue level is deprived of adequate oxygen) which leads to euphoria.
At high altitudes (above 10,000 feet or more), the pressure is so low that breathing will cause oxygen to diffuse out of your blood; you can breathe as much as you want but the partial pressure of oxygen in your blood will never be higher than the partial oxygen pressure in the air. This is why oxygen masks are necessary in cases of flying in non-pressurised aeroplanes (deliberately so or in a state of decompression as in an airline aeroplane).
Most people who are affected by hypoxia or lack of oxygen at altitude have a general feeling of elation or euphoria and think everything is fine.
Thus oxygen deficiency causes the onset of euphoria, such as in excessive drinking of alcohol or drug intake, especially recreational or illegal drugs.
That could be why a drunk of drug addict (when on a 'high' or euphoric) believes he or she can do 'anything', and with heedless recklessness.
Sometimes being in a state of euphoria can bring about the opposite effect, such as stupor, depression, disorientation, hallucinations and confusion.
One could quite easily say the outcome of the recent GE14 put Pakatan members and supporters in a state of heightened euphoria. Their joyous moods continue until even now.
But while most Pakatan-eers are joyous, deliriously happy and celebrative, one or two have swung the other way, becoming numb, depressive or very quiet.
Take Lim Kit Siang for example - from his normally vocal vociferous nature of spewing constant streams of pompous political policy (or takes) on everything and anything, he has recently become very quiet, even keeping mum when Mahathir recently broke Pakatan's manifesto promise of the PM not having any other or additional ministerial appointment, for example, that of Education Minister, until he (LKS) was asked.