Not only are JW's 'separate from the world' (everyone outside their organization), they are also isolated within their organization. Even though there is much association, meetings, get togethers, Bible studies, etc., there is also a sense of isolation.
Why do some JW's feel isolated, alone, and lonely? Because JW's must all 'speak in agreement'. They must be 'like minded'. Even though they say their beliefs are 'the truth' and all other religions are 'false', the reality is that unity of beliefs is far more important than 'the truth'. The best way to maintain unity, is for the Governing Body of Jehovah's Witnesses to tell everyone what the Bible means. Whether they are correct or not isn't as important as being united.
That's why some JW's are very lonely and isolated. They cannot 'run ahead' of what the Watchtower tells them. They must follow the rules and agree with doctrines, - even if they are not totally convinced. If they have nagging doubts, these must be kept to themselves. If a JW were to think differently than the majority (who blindly agree with the Governing Body's wisdom), they are thought to be mentally diseased, - or at least heading in that direction. Watchtower Dec 15, 2009, Article: Make Your Advancement Manifest. Watchtower Sept 15, 2002, Article: Keep Practicing the Things You Have Learned.
Thus when a JW has serious doubts about their faith, they can not discuss their concerns with anyone. If they talk with people outside the organization, they are a traitor. An active JW would never risk harming the organization by saying anything negative to outsiders.
JW's cannot freely discuss their doubts with insiders either. Active JW's are trained to report any member who disagrees or says anything negative about the organization. That's why it's risky business to confide in your friends, - even if it's a spouse or close family member. One never knows if someone will turn you in. The punishment for disagreeing with the organization can range from a friendly warning to excommunication. Disfellowshipped persons are to be shunned by all other JW's (with rare exceptions). See Apostates