Vision, hearing, smell, taste, touch: In certain ways, all these senses are the same. They all transduce stimulus energy into neural impulses. They are all more sensitive to change than to constant stimulation.
If you are bored with your relationship or your spouse/friend is bored with the relationship, change something. Change anything. Do you want him to notice you the way he used to, change something. He may not be able to put his finger on the change, but he will know something is different.
A subtle change is a good way to spark interest.