It is often said by those of the appropriate religions that God is all powerful. A common question asked of such people then is "If God is all powerful, can he make a stone heavy that even he cannot lift it". The most common response is "Yes he can, but then he will lift it anyway". It is often said that Love can do anything. So the obvious question is "Can love destroy itself". That is, can a love create a countering force powerful enough to destroy it. This may seem like a purely theological question, but in fact it's a completely practical one.
If one falls in love can one, using the power of that very love, destroy it if, say, the loved wishes it such. If one loves another truly, wholly, and unconditionally they, lover, will do whatever is believed best for them, the loved. What if the loved then is happy - contented with another for instance. Assuming they are worthy of said love they should wish the lover only to stop loving them, so that said lover can move on and live a happy life. This is, sadly, all to common a story. So by asking whether love can destroy itself I ask the question, is there salvation from this situation... a way out.
This question I feel reaches to the heart of the definition of love, and I think the problem is thus. No love is truly pure. If love were truly pure then certainly this should be possible. There are no relevant forces besides the desire to do as the loved wishes. Such a love though is none of common, healthy, or sensical. In reality Humans are nothing but completely selfish creatures, driven by human passions. Thus love is really a secondary emotion, begat of a desire to impress, the hope (whether rational or not) of getting something in return. It may be a truly deep hope, one which consciously is completely missing, but still lies deep in the sub conscious, where it is so hard for reason to penetrate.
Now this has not yet answered the question, for though Love is begat of other emotions, we have long since proved Descartes order of perfection false, and thus there is nothing to say that Love is not stronger than these other emotions. The problem, rather, is that though love can destroy itself, it cannot so easily destroy it's wellspring... and so it always returns, to be beaten back again. This is why the unrequited lover is always tormented, because as a lover this person's heart is never truly pure, and the source of the Love still exists, no matter how hard they may try to extinguish the love.
Consider for a moment, a diamond. A diamond has a fairly simple and extremely strong structure due to high interconnectedness. Such a structure does not spring into place all at once, it must instead be built a few atoms at a time. This can be described in terms of energy, by noting the energy required to float enough particles unattached next to each other, and get them all to drop at once, forming a perfect layer. After consider this it becomes obvious that this is entropic impossibility. Instead a diamond must have a slight imperfection, a dislocation in the perfect structure such that it can be built on slowly from this point of imperfection.
The story of the unrequited lover is like that of the diamond. The diamond, though seemly perfect, must have an imperfection to form... a root, a source. Same to with the lover, who requires a source of love, an imperfect thought or desire. To be clear, I speak of perfection here only as an explanation, as I do not believe in such a concept myself in any real sense, the important feature here though is that nothing of such beauty can form without these dislocations and imperfections... for they are the source and the way it grows.
So the story of the unrequited lover, while sad, is (under this theory) not a story of purity, but a story rather of constant impurity re-spawning the love, like a mote of dust in a cloud, their desire for something acts as a nucleation point, forming droplets over and over again no matter how many times it rains, the water evaporates, and the process repeats. This means that, sadly, that while love is strong enough to overcome itself, it cannot stop future love except by destroying the mote of impurity, the nucleation point. To do this though is to destroy the lover completely, for how does one completely destroy desire? Viewed in a different light, to achieve this is in fact to to achieve nirvana. Something not viewed impossible, but something many strive their entire lives for and fail at. So, no wonder the world is strewn with unrequited lovers, fretting over their pain.
Just a random meandering, that's all