Javed110: I dont think that "you must experience" the extremes. You dont neccesarily have experience hatred to appreciate love. You dont necessarily have to experience defeat to appreciate victory. You dont necessarily have to experience pain in order to appreciate pleasure. On the other hand, as you mentioned, contrast plays a big role in appreciation. I agree that there is no white without black. There is no day without night. You just have to know they are there to appreciate the opposite.

Love needs hatred.
Victory needs defeat.
Pleasure needs pain.
You must experience and accept the extremes. Because if the contrast is lost, you lose appreciation; and when you lose appreciation, you lose the value of everything. (A)

Pain is a function of love. Pain is the best indicator for love too. When you are separated from your beloved you feel PAIN. The degrees and different types of pain experienced by one reflects whether the love was true or not. To measure the quality of your love will depend on the amount of pain you endured.

love and pain are yin-yang emotions. one cannot exist without the other and like you said, the balance does swing. but perhaps pain lessens when you have no regrets? when you have done all you could and you could do no more. there will still be pain but there is also the knowing that it is time to let go and see what your naseeb brings

sometimes you can love but only for a moment - and perhaps that was all it was supposed to be; a moment. a good relationship does not necessarily mean it will be a long relationship.

sometimes longevity and love cannot co-exist and the pain comes from trying to make something that burned out or had its moment of madness into something longer.

However despite the potential risk that love may be lost in the future, there are many worthwhile lessons that the couple discovers about love and life in general. Falling in love always entails risk or uncertainty that the relationship will not sustain in the long term regardless of the amount of initial trust a have for each other. Love can end in pain, misery, and heartache but can also result in utter happiness. Sometimes being in love can act as a stepping-stone, or a doorway passage into another world, that you never know what was out there. If the relationship dissolves in the future, he or she can at least find solace in processing a? lesson learned? database of mistakes made in the relationship for critical application in a potential future relationship. In short, having loved and lost is better than never having loved at all because have love is one of the few things that teaches a person the spiritual significance of life, assist one in avoiding unproductive or harmful personal activities and provide valuable relationship and communication skill. (A)

I seem to get more pragmatic by the day - which isn't doing wonders for my writing.. but anyhoo - pleasure and pain must coexist for either to have meaning. Beyond that reality, if we're talking of romantic love, solid, good, happy relationships do exist albeit they are few in number.

But with God's grace, being able to speak for myself here, I think that loving relationships have the ability to dull the anguish of painful memories. That said, the better your relationship, the more sensitive you could become to even little amounts of pain - being no longer used to it.

Or, you could learn to accept that little shots are necessary and therefore take everything with a sack of salt, and relish the twang rather than weep over the lack of perfection. Do I make any sense?

I'm no psychologist or philosopher, but here is what I think.
Love, in its pure form, is always pleasure. The concept of pain arrives when impurities such as expectations start showing up. Now the question arises, does pure love exists? I dont know. Its a beautiful concept but very hard for me to grasp.
To answer your question, yes, it is bound to swing between pleasure and pain. Whenever there is an element of pain, we either try to put more weight towards pleasure side by getting pleasure out of pain or reducing weight of pain by focussing on pleasures and ignoring pain.