Have you noticed a painfully revealing phenomenon? The more we give to friends, the less they seem to cherish it in return. At first, people are overwhelmed with gratitude; later, your help becomes “only what’s supposed to be.” If you don’t help even once, the other person may get angry—almost as if you’ve betrayed something. I’ve fallen into this trap myself: the long-term result of always being the “nice one” is that gratitude shrinks, yet expectations grow. In fact, this isn’t cold-heartedness. Behind it is a little-known but extremely practical psychological principle called the Law of Diminishing Sensitivity (Weber’s law). Once you understand it, you don’t have to force yourself to tough it out with many interpersonal problems.

First, let’s talk about what the Law of Diminishing Sensitivity actually is. Simply put, people’s initial reaction to any stimulus is very strong, but the more it repeats, the brain “gets used to it,” and the response becomes weaker and weaker. The first time you receive a gift from a friend, you feel happy; the second time, you can still feel moved. But if it happens every day, it just stops meaning much to you. In psychology, this is called “stimulus adaptation”—in reality, it’s the brain’s energy-saving mode. Otherwise, if every good thing kept triggering the same level of sensitivity, life would have long been too busy to handle.

Even more interesting are the neuroscience explanations. Good things at first bring a large burst of dopamine, making you excited and happy. But your brain’s reward system quickly learns to predict that kind of good event. When it finally happens for real, the pleasure isn’t as strong. This is also why the honeymoon phase fades—once the same kind of actions come later, you no longer feel that electric current-like stimulation. Economics has a similar idea called “diminishing marginal utility”: with the same input, the early return is high, but as you add more, the stimulating payoff gradually gets smaller.

How can science verify the Law of Diminishing Sensitivity? The most classic is the weight test. Have someone hold a 400g weight, then switch to 405g—most people can feel that it’s heavier. But if the first weight is 4000g and you only add 5g, almost nobody can tell the difference. The feeling is basically a threshold game. In 2016, a UK psychology journal published an experiment in which participants received “little favors” at different frequencies every day. The results found that everyone’s novelty toward high-frequency rewards disappeared quickly. By contrast, after reducing the frequency, people valued the rewards more and remembered them more deeply. Disturbing to think about—sometimes, less really is more.

So how do you reverse this “diminishing effect of giving”? The first method is to deliberately control how often you give, so that kindness becomes scarce. Don’t go all-in from the very beginning, especially with new relationships. Low-frequency, high-quality help is far more likely to be cherished than being available on call every day. When friends ask you for help, occasionally take the initiative, and occasionally say, “This time it’s a bit inconvenient, but I’ll do my best next time”—instead of draining the feeling, this can help them regain a sense of expectation.

The second method is to create small changes and increase unpredictability. The brain loves the effect of surprise. Don’t mechanically repeat the same kind gestures—regularly switch up the style, and use different ways to express care. This is especially effective in relationship management, team motivation, and parent-child interactions.

The third method is to elegantly hold your boundaries and learn to refuse appropriately. Every act of kindness should make it clear to the other person that it’s not something that comes easily. Setting boundaries is actually about maintaining your emotional “psychological threshold.” Sometimes it’s only by occasionally saying “no” that interactions stay fresh and respectful.

Finally, I want to say this: don’t treat the Law of Diminishing Sensitivity as a defensive shield in social interactions. A true expert doesn’t use it to scheme against others; instead, they regulate their own sensitivity and choose where to invest their giving. Put your kindness and energy into the people and things that are most worth it. Don’t let your sense of self-worth depend entirely on other people’s feedback—and don’t treat good intentions like “hard currency” that you discount every day.

If you can apply the Law of Diminishing Sensitivity to self-awareness, every proactive act of kindness will feel more substantial. Carefully manage your giving threshold: be sensitive when you should be, and be less sensitive when you should be. No matter how others respond, they won’t be able to take away your initiative in relationships.