Pterist suggests analyzing why that JW joined the religion in the first place.
Although that may be helpful in some cases, I wonder as a general rule to what extent the reason for joining is actually relevant to their reason for staying in.
For example, a person might be drawn in by the end times chronology, but it doesn't take long to see that the GB keeps changing the dates, redefining terms like "generation," and so on.
You'd think that such a person would recognize the bait and switch and quickly get out.
But often they remain convinced it's "the truth" and that the GB speaks for Jehovah despite all the evidence to the contrary.
Something else is keeping them in.
Maybe it's the sense of belonging to the group or the excitement at having knowledge that outsiders don't have or the fear of losing family and friends or being destroyed at Armageddon if they leave or even waver...
In addition, a high percentage of JWs aren't converts at all.
They are born-ins or raised-ins.
The issue with them isn't why they joined; the issue is what makes them stay.