Some past friends have continued on steadily with some ups and downs. Some have walked away and stayed away from the faith that was a part of their lives when younger. Some walked away but came back later when their way of doing things produced bad results. Some found a faith they never knew before and are thriving in it today.
One very common element in almost every (perhaps every) situation: The responsible adults in the lives of these friends when they were younger. Some adults lived consistent lives of faith, some never pretended to have any faith in God, and some had a major breakdown in the way they lived that left a significant impression on the child or youth.
Those who looked to adults as their paradigms risked major disappointment. Those who looked to God have sometimes had difficult lives but were never disappointed by their role model.
Moral?: People mess up. God does not. Keep your focus on God.