When you get away from a difficult situation, it can become simplified and even romanticised in your mind, leading you to go back to give it your best shot.
However, once back, reality sets in big time and you realize the same old barriers to acceptance remain.
It's spookily akin to people whose intimate relationships are endlessly off-then-on then off again and so on. Some perfectly normal needs are being accommodated - but if the needs are in conflict, people commonly cope by oscillating "between" the needs.
The two needs that seem to have the greatest push and pull on those affiliated through family with strict religious groups are, firstly the need to have a safe and secure place of belonging and secondly the need to critically appraise one's beliefs.
These two core human needs are vulnerable to being in opposition. The former is deeply emotion-based, the latter, cognitive and concerns making sense of what one is asked to believe.
It is clear that, if your connection to the group is primarily through family and especially parents or spouses, your ability to get your cognitive needs met will be sorely tested. In contrast to what one's religious leaders intone, problems with belief are not "settled" through discipline and threat. As a result, yo-yo-ing occurs. Very human indeed. I suspect that, were it not for these ties and bonds, kingdom halls - and, to be fair, meeting places of many strict religious groups and institutions - would empty very quickly.
Going back to get one's approval needs met is understandable I suppose - but it's a hell of a tortured way to live one's life.