mills of the gods grind slowly
One's destiny is inevitable even if it takes considerable time to arrive. For example, I'm sure he'll be wealthy one day, though the mills of the gods grind slowly. This expression comes from ancient Greek, translated as "The mills of the gods grind slowly, but they grind small." In English it appeared in George Herbert's Jacula Prudentum (1640) as "God's mill grinds slow but sure."