First of all, I want to say this: Love is love is love.
To this whole good and bad and evil nonsense: there is no such thing as relative good and relative bad. There is universal good, and universal bad. Just because your culture or upbringing tells you it is or isn't wrong, does not make that right. Good and Evil is an objective constant; there are no variables.
Okay, now relative emotions. Yes, these are certainly relative and wholly dependent upon the person and situation. Will one event make you happy, and another sad? Of course; it's all about perspective and certain points of view. But to say that living in and of itself is one long thread of slightly-negative with certain events bringing you up to a happy line until you just come back down to a life of pessimism is... narrow but, most of all, sad.
It is as one says: relative. I do not mean to cheapen your existence of constant negativity; if that's the way you want to live and experience life, then by all means, have at thee. That said, life is what you make of it. It can be a constant thrill, or a constant reminder of how much things suck. It's all down to the person, and nothing we do or say can change that about them.
But these spikes of emotion? Certainly they can be just that, spikes. But how can one say that that rise or fall cannot become their new "baseline"? Again, life, living and emotional bearing are all what we make of it. There is no scientific formula to how we as an individual and a species bear our loads of baggage or relieve ourselves from it. If we choose to, we will, and can.
Now, looping around: love is love is love.
We experience what we feel is love, which is lust, at all manner of the day. This is, as through my definition, a rush in which we simply want to lay with the person. Another way of looking at is is the thrill in which we imagine ourselves being with that person, say, romantically. It's a momentary thing, a flash of brilliance in what we perceive to be mundane, or normal. It's why cheating happens-- we see a flash of something and want to grab onto it.
But love transcends the grey, the flashes, the mundane, the lust. Love is... love. It is indescribable, undefinable, unformulaic, and unimaginable. It is a feeling in which we suddenly become god in our own universe, and we make of it as we will. Love doesn't cheapen, it doesn't become lax or weak or something less of what it used to be: that's us. We as humans let love dim and fade away, or we let our vision skew away from it. But love will always be, and burns just as brilliant as it always will.