In the event of great exultation, a person might feel he has suddenly reached a very high plane of spiritual potency.
Indeed, any imbalance in the mixture of the worlds is apt to cause trouble.
One may learn this lesson from the instance of Rabbi Elimelech, who ordered his Chasidim to refrain from wine and liquor during the latter part of Succot and especially on Simchat Torah–and this precisely because Simchat Torah is a special time for joy in the Torah.
According to Rabbi Elimelech, if the joy of Simchat Torah is mixed with half a bottle of vodka, there may be some difficulty in distinguishing it, because the sensations are similar.
As one of the Sages remarked, a person who takes pleasure in good food on a feast day is often enjoying his belly and not the holiness of the occasion.
Thus the feeling of joy in some outer spiritual circumstance will have its parallel in a physical source.
Because the physical sensation can be the same for both, there is a lot of room for imagination and error.
A person can imagine he is on some high plane of sanctity and actually just be puffed up with pride.
The sensation of spiritual achievement may very well be no more than an enhanced appreciation of one's ego.
To be sure, there are instances when the distinction is so grossly obvious that a person has to be cunningly able to deceive himself to get away with the fraud.
–Rabbi Adin Steinsaltz
From In the Beginning by Rabbi Adin Steinsaltz