What you did in the start of the relationship to make your partner fall in love with you is what you need to continue to do. If you stop doing those things, resentment will fill in the place where love once was.
If you originally went out on a date once or twice a week and now never do and wonder why your relationship is lacking passion and romance, maybe thats why. The courtship never ends, you need to continue judging your partners attraction level and keep it as high as possible. Continue making them fall in love with you everyday.