1. Proper concentration when praying may make the difference between life and death.
2. The Gemara discusses the curse to the descendants of Eli, and how they can avoid an early demise.
3. Rabah and Abaye were descendants of the house of Eli.
4. Hashem knows and understands everyone's thoughts and actions.
5. The Gemara lists the national tragedies that happened on our public fast days.
A BIT MORE
1. Rebbi Meir: Two people with the same deadly sickness or same death sentence may both pray for their salvation. It is possible that the one who concentrates properly will be saved, while the one who does not concentrate properly will not be saved.
2. Rabah: They should learn Torah. Abaye: They should learn Torah and be active in helping others.
3. Rabah followed his advice (see #2 above) and lived for forty years (instead of the eighteen-year life expectancy for the house of Eli), whereas Abaye followed his own advice and lived for sixty years.
4. This is as the verse states, "The One who created all of their hearts together, He understands all of their actions."
5. For example, on the ninth of Av, both the first and second Batei ha'Mikdash were destroyed, Beitar was captured, and the area of the Beis ha'Mikdash was plowed over.