How we change what others think, feel, believe and do
A way that members of groups are retained is by assuring that they never reach completion, and that they are constantly striving for more.
Jonathan Swift said, 'It is better to travel hopefully than arrive'. Hope is a key part of striving, along with a belief in better things to come for those who strive.
The group typically dangles a carrot in front of the person in the form of the promise of enlightenment, riches, being 'saved' and so on. Framing what the person once thought as unattainable as now a real possibility awakens a deep longing in them. The thought of escaping the drudgery or demons of their everyday existence to a perfect paradise is amplified by the group who, initially at least, make these ultimate goals seem realistic and attainable.
Early successes serves to bond the person further into this goal and serves to amplify their hope. This may often be created by a self-fulfilling prophesy - if you believe in something enough, it is surprising what you can achieve. The 'low hanging fruit' of early wins are particularly useful in building hope, whilst it is forgotten that later wins are increasingly difficult. Even mystical experiences can appear as prayer, mediation, fasting and a poor diet lead to hallucinations. Extreme groups have even been known to feed their members hallucinogens.
A sequence of rewards
A more controllable form or reward is given with promotion within the group to higher levels, for example by giving them a new status name (acolyte, traveler, master, manager, director, etc.) or by giving them new authority within the group. At each level, they may be given new secrets or taught more of the group's special language. They thus may join the game of playing 'more perfect than you' with lower orders in the group.
Individuals are constantly encouraged to constantly push towards this ultimate but unattainable perfection.
The leader knows perfection
The leader of the group is the ultimate judge of what perfection is and how well or badly the person is progressing towards it. Thus their strivings and even real achievements may be downplayed - not enough to completely put them off, but still enough to frustrate and reframe the hope. The leader may also be framed as embodying perfection. Thus they can do no wrong and their word cannot be challenged.
Imperfection into punishment
The unattainability of the ultimate perfection can then used to induce guilt and show the person to be sinful and hence sustain the requirement for confession and more ardent obedience to those higher than them in the group's order of perfection.
Not being perfect may be seen as deserving of punishment, which may be meted out by the higher members of the group or even by the person themselves, who are taught that such atonement and self-flagellation is a valuable method of reaching higher levels of perfection.