From a systemic-interactive point of view, love is a common interaction. Nevertheless, its mechanism is commonly misunderstood.
An interaction is an exchange of something between two entities. There are two parts: what the subject receives, and what the subject delivers (you are the subject because you are assessing the interaction, and she's the object of love).
The most common notion of love is love as receiving. The subject gets attention, care, sex, etc. It cannot be controlled, ergo, it is a passive form of love. It does not require nothing, it is egoistic, and tends to enforce self-esteem. People commonly thinks of this variant as the meaning of love. Sadly, if the subject is focused on this perspective, love will dissappear for sure. It is not really an interaction, so, the object could soon get tired of giving and not receiving.
The other perspective is love as giving. Of course, this is absolutely controllable, it is an active form of love, and it requires effort. It does not give nothing to the subject, nothing, except the pride of giving. It is not easy to perform, requires patience and constance. Of course, the object of love will feel pleased.
But here's the magic of human interaction: any action creates a tension, and our human nature demands us to relieve tensions in order to survive. So, if you give love, the other person will feel good, and if she's a normal, sane and mature person, will feel grateful. Gratefulness can be relieved only by mirroring the action, that is, performing an equivalent reaction.
The consequence of this natural behavior causality is obvious: if the subject receives love and returns less than received, the object will soon lose interest and the interaction will end. On the contrary, if the subject gives more than received, the object will get permanently engaged in the relationship.
But wait, you don't need to wait until receiving something to start reacting. You can be the causal generator. You can start giving and always give more than received (at a certain point, you will feel that her life is more important than yours, that's just part of the process, but it does not imply stop loving oneself: just having a lower priority than the other). As said, if she's mature, love will never end. Eureka, that's the real recipe for love: choosing a sane and mature interacting partner, and always give more than received. In fact, that's the same recipe for economic development and any other interaction. You can find all this on my last book.