Loyalty
Loyalty is one of those things we crave in life but we don't always find it when we think we need it. Suppose you meet some new people, become friends with them, and start doing things with them. Until you have shared some real, true bonding experiences with them those people may not be as loyal to you as you think. For example, they may choose to do things with older friends (or family) before they do anything for you. They may be less inclined to risk their lives or getting hurt to protect your property. And so on.
At some point we all form emotional bonds with other people. Followers may become loyal before leaders; in fact, followers tend to be more loyal to their leaders than leaders to followers. A leader may sacrifice the best interests of a single follower in order to protect the interests of the group -- or, worse, the leader may only put his own selfish interests ahead of everyone else's (that is a pretty terrible leader).
Loyalty is based upon shared respect and an expectation that the person to whom you are loyal will help you and protect you; less often loyalty is based on a sense of duty, such as the loyalty of a subject to a prince or king. A "loyal subject" is someone who will defend the country against invasion and destruction. A loyal citizen puts the interests of the nation ahead of his own interests.
Loyalties may change for any number of reasons but I think the most common reason for a change in loyalty would be the failure of a leader or group to help and protect the person whose loyalties have changed. That is often cited among the grievances of peoples who protest against their leaders, perhaps even scheming to abandon their old loyaltles for new leader and nations.
If you have ever questioned the loyalty of your friends and acquaintances then you understand how precious loyalty can be and how hard it is to earn strong loyalty. If you don't show other people you are worthy of their loyalty and respect they are less likely to give you that kind of loyalty and respect. The most common mistake overzealous people make is to confuse fear with loyalty or respect. Weaker people may do something out of fear rather than out of loyalty or respect.