Dr. Phil Mc Graw said that women fall in love with their ears, guys fall in love with their eyes.
I was/am in good relationship and I know that guys are in the dark how women think but it's simple... constant reassurance that you love &miss her, showing your eagerness to make her happy& willingness to listen.
For guys, beautiful partner, good sex, a loooooot of ego stroking, motivation, seeing satisfaction from his partner... what else?