I don't understand this passage in the Talmud:
The righteous outside of Eretz Yisrael will be resurrected and roll [until they reach Eretz Yisrael]… Rabbi Abba Salla Rava strongly objects to this: Rolling entails suffering for the righteous. Abaye said: Tunnels are prepared for them in the ground. Karna said… Our Patriarch Jacob knew that he was completely righteous, and that the dead outside of Eretz Yisrael are resurrected [anyway], so why did he trouble his sons [to bury him in Eretz Yisrael]? Because he thought he may not be worthy of the tunnels. (Ketubot 111a)
If Jacob "knew" he was "completely" righteous, why would he worry that he "may not be worthy of the tunnels"? What's the logic?