Recently, I discovered a particularly interesting phenomenon—many relationship troubles can actually be explained by a psychological principle.

Have you ever experienced this: at first, helping a friend, they are incredibly grateful. But after helping more and more, they start to take it for granted. One time you don’t help, and they get upset. I’ve also fallen into this trap; during that period, I kept trying to be the nice guy, only to find that gratitude decreased and expectations grew higher and higher. Later, I realized it’s not human indifference, but a deep mechanism in our brain that’s at work.

There’s a rule in psychology called the Weber-Fechner Law, which explains this. Simply put, your initial reaction to a stimulus is very strong, but after repeated exposure, the brain “gets used to it,” and the response weakens over time. It’s like receiving a gift for the first time makes you very happy, but by the tenth time, it’s no big deal. This is called “stimulus adaptation,” a natural energy-saving mode of the brain. Our cognitive resources are limited, so if we were sensitive to all good things equally, we’d be overwhelmed.

From a neuroscience perspective, it’s even more interesting—initially, good things release a large amount of dopamine, making you excited and happy. But the brain’s reward system quickly learns to predict these good things, so when they actually happen, the pleasure isn’t as intense. That’s why the honeymoon phase passes, and doing the same thing again afterward doesn’t feel as exciting. Economics has a similar concept called “diminishing marginal utility”—the same investment yields high returns initially, but as you add more, the stimulation from the gains gradually diminishes.

A classic experiment vividly illustrates the power of the Weber-Fechner Law. Researchers asked participants to lift a 400-gram weight, then a 405-gram weight; most people could immediately feel the difference. But if the first weight was 4,000 grams and only increased by 5 grams, almost no one could tell the difference. The perception becomes a threshold game. Psychologist Ernst Weber discovered that the stronger or larger the stimulus, the lower the discrimination ability. A 2016 experiment in a UK psychology journal confirmed this: participants received different small rewards daily, and everyone quickly lost interest in high-frequency rewards. But when the reward frequency was reduced, they valued and remembered the rewards more. Sometimes, less really is more.

So, how can we reverse this “diminishing returns of giving”?

The first trick is to deliberately control the frequency of your efforts, making kindness scarce. Don’t give everything at once from the start. Especially in new relationships, low-frequency, high-quality care is more likely to be appreciated than being there every day at a moment’s notice. When friends ask for help, occasionally take the initiative, and sometimes say, “It’s not convenient this time, but I’ll do my best next time,” which can rekindle their anticipation. This is the clever use of the Weber-Fechner Law in relationships.

The second trick is to create small changes to increase unpredictability. The brain loves surprises. Don’t mechanically repeat the same kindness; instead, regularly switch things up, use different approaches—even just changing how you show concern can be very effective. This works especially well in managing relationships, motivating teams, or even in family and parenting.

The third trick is to gracefully maintain boundaries and learn to say no appropriately. Every act of kindness should make the other person realize it’s not easy to come by. Setting boundaries is actually about maintaining your emotional “psychological thresholds.” A sense of boundary in a relationship is what makes it truly enduring. Even occasionally saying no can keep interactions fresh and respectful.

Ultimately, the core of the Weber-Fechner Law isn’t about calculating or manipulating others, but about learning to regulate your own sensitivity. Make deliberate choices in giving, and focus your kindness and energy on the most worthy people and things. Don’t let your sense of self-worth depend entirely on others’ feedback, nor treat kindness as a hard currency that’s always on sale. If you can apply the Weber-Fechner Law to self-awareness, every act of initiative will carry more weight. Carefully manage your giving threshold—be sensitive when needed, dull when appropriate. No matter how others respond, you won’t lose your initiative in relationships.