I gather that some people, especially those under the age of 45 or so, feel that they know when a relationship is no longer worth preserving. They met, they were attracted to each other, they liked each other but now a decade or so later, the positive feelings are diminished. The idea seems to be related to magnetic fuel tanks. My tank is drawn to your and vice versa. However, we have been attracted to each for a long enough period that I am just about empty and so are you. What to do? Have the courage, emotional, logistical and financial to part. Maybe we will each find others with longer lasting magnetic pull and bigger supplies of love and attraction.
I think that is a mistaken picture. It doesn't fit the way the world is and it probably leads to unnecessary waste of feelings, energy, and money. My picture is that, while it is true that we aren't strongly attracted to everyone, we do as much to create and nourish attraction and compatibility as stumble upon it.
So, in my picture, not feeling a thrill is a sign that thrills need to be created. I think they can be. I think practice can improve our thrill-making. We can create attraction and appreciation more deeply, more memorably, more quickly, more effectively if we practice. If you are the very rare woman like the character in the tv show "Private Practice" who says to her lover,"Take off your clothes and get on top of me", you may find that something a little softer and less imperious adds a light to your lover's smile. If you are the more typical person who would be embarrassed to say something like that, try delivering the line straightforwardly and honestly with no smirk or frown.
Older people know that it is not the tight clenches and embraces that make the most difference. There is often more impact on your day and your partner's from the first words out of your mouth in the morning or the expression on your face when you first lift your head. So, if I don't feel a thrill or a jolt of gratitude, it is probably time for me to give an affectionate pat or bring a cookie along with the usual cup of coffee. Experienced re-writers know that a change in the script is often first met with nothing. Your witty or loving or appreciative remark or facial expression might be overlooked. It might be met with suspicion ("What is he/she trying to pull now?") But with a little energy and determination and imagination, you can probably give your relationship a new coat of paint that will brighten more than one life.