One way to avoid self-righteousness when your brother falls is to keep in mind that each of us is capable of the worst evil, because we are all equally fallen. That’s why Paul said, “Brothers, if anyone is caught in any transgression, you who are spiritual should restore him in a spirit of gentleness. Keep watch on yourself, lest you too be tempted” (Gal 6:1) and “Therefore let anyone who thinks that he stands take heed lest he fall” (1 Cor 10:12).  See also 1 Cor 9:27.