I do get a strong mental clarity when I go very low carb. I wouldn't describe it as euphoria. I have read of others who truly benefit from a mental health standpoint from very low carb diets. It evens out their emotions. This is a far cry from a euphoric high, unless finally not feeling depressed and in a mental fog could be described as euphoria.
I would doubt that if you are seeking a feeling of being high that you will attain it like you did at first. It was probably just the newness of suddenly not being clouded by the effects of grains and bad oils and getting over that initial low-carb funk. Your brain at last getting what it needs with nothing in the way.
Female, 5'3", 50, Starting weight: 163lbs. Current weight: 135 (more or less).
I can squat 192.5lbs, press 75lbs and deadlift 210lbs