The cost of complacency is missing out on the emotional rewards of success, from taking risks that trying something new can foster. Can this in fact generate a staleness and bitterness in the mind that can even turn dark in the form of jealousy and even hatred for those with a genuine zest for life?

This indeed can happen, but it must be the case that at some point there is some kind of awakening from complacency, or at least a lessening in degree, because complacency means exactly what it is defined as: "The absence of caring." So any kind of dissatisfaction that may result from being chronically complacent and then having life pass one by or miss many opportunities others may have pursued while one was seemingly lazy and indifferent, may well be regretted later and seen as a failure to embrace life’s possibilities and do some hard work to gain the rewards others enjoy now, whereas the complacent person in that chronic state may have little to show for large spans of time, but that is the intention of creating complacency in a purposeful fashion. It can be a state that serves as a reward when people have done their best and given their all for an enterprise and then reached a state of resolution or conclusion for the project and can stand down for a time to rest and recuperate. Being complacent during such an interval is a luxury for most, but it is self-selected and self-imposed and not manipulated to be created within a person’s mind. That is quite a different prospect and is an evil manipulation because it robs a person of potential rewards and diverts them from what they would be doing otherwise left on their own, and so it is a subversion of the life of another, an invasion of their sovereignty, and a manipulation to change the destiny of their life in some fashion. All of this is non-divine and, in effect, a criminal undertaking.