Do you believe in such a thing? It's interesting how when you love someone, that love can be absolutely selfish; or, it can be sincere.
For example, let's say that your best friend is going to leave the country and study abroad. You get upset and don't want her to leave you. Now this is called selfish love, it's because you love yourself more than the person that you claim to love. If you sincerely loved her, you would have been happy for her and wanted her to be happy and gain as much as she can out of this experience. Some girls even get upset when their best friend gets married, thinking that she'd leave them and live her life with her husband. Or even if a friend wasn't there for you when you needed her/him, you get all upset instead of thinking of what they were doing.
Another example is a person's death. You get upset that they left this world and left you. Instead of you being joyous for their gaining a place in Heaven, you act on your selfishness and get upset, making them get tortured in their grave.
Now this is not to say that such actions cannot be justified, for we are all human beings here with emotions. We get jealous, upset, happy, excited, depressed and so on. I've been told that the only time such an action of getting upset and the such can truly be justified is when the person you love is hurting themselves by doing something wrong. Like doing illegal things for example, or perhaps engaging in sinful acts.
The true and sincere love is very hard to find, and very rare. It's the kind of love where a person, even in their worst moments, puts you before them. This can be argued of course, where asking for another's help if you needed it is crucial in such situations especially since the other party would feel much better if being in the know at the moment rather than after it (that is, if it was their feelings that would be considered).
Relationships between the opposite sexes in our society are mostly based on gaining a feeling of security and are thus selfish. They are not, in any way, sincere. Think about it, these things are usually started in order to gain a feeling of security in order to cope with the hard times that are went through. Those relationships almost never work, even if they did end in marriage, for they will be rocky ones.
True love between two members of the opposite sex is very rare, but it does exist. Fishing for a good partner that doesn't base feelings on one emotion (most probably, security) and puts their partner in front of them in everything, is absolutely honest with them and trusts them so much is what makes true love the most seekable feeling ever; it means respect, honesty, trust, security and comfort. That, among other things. Some people settle for a few of those components, and try and make things work out. Others have them all, and those are the luckiest.
That's the difference between selfish and sincere love as I understand it, others might have different perspectives.
Breaking the Chains:
"Never pretend to a love which you do not actually feel, for love is not ours to command."