How can one reconcile long working hours and feelings of exhaustion with performing prayers on time, especially Fajr and Asr prayers, given that sometimes an alarm clock is used but one does not wake up?

A Muslim who has no valid excuse must perform every obligatory prayer at its prescribed time and take the necessary means to do so. If he does so and is then overcome by sleep, there is no sin upon him, as the Prophet (peace be upon him) said: "There is no negligence in sleep; rather, negligence is in wakefulness."

However, it is not permissible to intentionally go to sleep when the prayer time is narrowing, as this leads to missing the prayer. Imam Al-Shawkani clarifies that the hadith applies to sleeping before the time narrows. As for someone who intentionally sleeps after the time has narrowed, knowing that the time will expire, he is sinful for abandoning the prayer.