Muhammad, anxious about his own eternal fate

Recently ran across this interesting hadith, which shows just how worried Muhammad was about his own eternal fate:

Narrated Masruq:

‘Aisha said that a Jewess came to her and mentioned the punishment in the grave, saying to her, "May Allah protect you from the punishment of the grave."

‘Aisha then asked Allah’s Apostle about the punishment of the grave. He said, "Yes, (there is) punishment in the grave."

‘Aisha added, "After that I never saw Allah’s Apostle but seeking refuge with Allah from the punishment in the grave in every prayer he prayed." 

Sahih al-Bukhari, Volume 2, Book 23, Number 454