Love?

What does love mean? until now i also donno how to define the meaning of love. Love look like something complicated, that we cant really know what to do in a relationship. people say that love is sweet and happiness but in seen like just for a moment. After long period the feeling no closer that last time. Like when start a relationship, There is a lot call, sms. keep thinking of each other, but time go longer the feeling not as intimate as before. Then will be suffer and etc. Until end of the relationship. Love go dying. How to save the relationship and remain like before? it's seen hard to do that.