Well, Love is something that you need to nurture. I am pretty sure every one will agree with me on this fact that no matter how good looking and smart person you are; if you fail to maintain your love, take a good care of it, you certainly gonna fail being happy in your relationship.
Now the question is how it should be nurtured?
I am glad you wanted to know that. All you need to do is to love your partner unconditionally and don't ever take each other's love for granted. Respect each other no matter what. It can be something they like, something they prefer, something they agree about; you have to respect that they like that even if you don't.
The most important thing is showing them that you love them. Remember your actions and your words should work simultaneously to prove that you are in love with them. Use romantic quotes and saying to express you love them them. Spend quality time with each other and give the maximum priority possible to each other.