Is it permissible to stop performing the Witr prayer after making fervent supplication in it and feeling at ease, even if the same fervor is not repeated on other nights, or must one continue to perform night prayers on other nights even without such fervor?

"Qiyam al-Layl" (night vigil prayer) and "Salat al-Witr" (odd-numbered prayer) are prescribed on a continuous basis, not merely when one intends to supplicate. Languishing during supplication does not justify abandoning them, for the Prophet, peace and blessings be upon him, said to Abdullah ibn Amr ibn al-Aas: "O Abdullah, do not be like so-and-so; he used to perform Qiyam al-Layl, then he abandoned Qiyam al-Layl."