Jesus addressed that question right after he warned the disciples not to turn back to Satan’s wicked world.
مَاذَا يُمْكِنُنَا فِعْلُهُ لِنَضْمَنَ أَنَّ ثِقَتَنَا ٱلرَّاسِخَةَ بِإِتْمَامِ وُعُودِ يَهْوَه لَنْ تَتَلَاشَى ؟‏