Your car rides on tires and is going nowhere without them. Your relationship with your woman rides on affection. You don't leave the tires off your car and just put them on when you want to go somewhere. They are always on and ready to roll. Similarly, affection should always be a part of time spent with the lady in your life. Hugs, gentle pats on the back, an arm around her shoulder, a little kiss on her forehead, holding hands, and saying "I love you" are signs of affection which should be sprinkled liberally throughout the week, using at least one a day. (You may think telling her you love her once, at the beginning of the relationship or marriage, settles that issue from then on. But you can't fill your car's tires just once, and count on them to never go flat, and a smart man knows to tell his woman often that he loves her, before their relationship goes flat.)
As with the necessity to rotate and balance your car's tires, it is also necessary sometimes to vary the routine with your woman. Before the usual goodbye peck on the cheek one morning, try holding her shoulders, looking into her eyes, pausing dramatically and telling her you love her! And any time the ride seems bumpy in your relationship, remember to air up the affection.