Our innate instincts are programmed to pay more attention to negative things (pleasure is great, but discomfort and danger can be life-threatening). This makes us naturally a bit pessimistic and paranoid, jealous and controlling. A great survival strategy, sure, but not a plus for relationship contentment.
Here are some suggestions for homemade gifts that enhance relationships by focusing on the positive, expressing appreciation and enhancing self-esteem. And they’re inexpensive or free!: