Hey there, Delilah-
Okay, I deserve severe punishment for that one. I don't even like that song...
If I'm reading you right, I think you're asking "if heaven is good all the time, can we even tell that it's good since we have nothing to compare it to?" I hope that's what you're asking, at least, because that's what I'm going to try to answer.
The fundamental principle here is opposition, which is a key point of Lehi's teachings to his son Jacob in 2 Nephi 2
. In part, he states:
11 For it must needs be, that there is an opposition in all things. If not so, my first-born in the wilderness, righteousness could not be brought to pass, neither wickedness, neither holiness nor misery, neither good nor bad. Wherefore, all things must needs be a compound in one; wherefore, if it should be one body it must needs remain as dead, having no life neither death, nor corruption nor incorruption, happiness nor misery, neither sense nor insensibility.
12 Wherefore, it must needs have been created for a thing of naught; wherefore there would have been no purpose in the end of its creation. Wherefore, this thing must needs destroy the wisdom of God and his eternal purposes, and also the power, and the mercy, and the justice of God.
13 And if ye shall say there is no law, ye shall also say there is no sin. If ye shall say there is no sin, ye shall also say there is no righteousness. And if there be no righteousness there be no happiness. And if there be no righteousness nor happiness there be no punishment nor misery. And if these things are not there is no God. And if there is no God we are not, neither the earth; for there could have been no creation of things, neither to act nor to be acted upon; wherefore, all things must have vanished away.
The idea is that without opposites, we have nothing to compare our experiences to. We can't know happiness if we don't know what sadness is like. We can't recognize peace without having felt anxiety or fear. In other words, if you only ate sugar all the time, you would have no clue what sour, or bitter, or spicy things tasted like. You wouldn't even be able to imagine them.
Now, if, perhaps, Heaven was a totally hunky-dory place, it might appear that we fall into the trap of diminishing returns. Our happiness flat lines, because it's expected, normal, and gets old and boring. Right?
I sure hope not! And I don't imagine it that way, either.
For one: This is the point of mortality.
I'm sure you've heard somebody say that we couldn't have progressed any further as spirits in the presence of God. Part of that is because we needed a body, part to be "free agents," and part -- this part -- to experience mortality
. I'm betting you have your share of depressing, saddening, or demoralizing experiences in this mortal life, and your question is one of the reasons why. By the time you make it to exaltation (very possibly a long way off, even after death), you'll probably have had enough pain, struggles, and setbacks to appreciate an eternity of happiness. Your mortality, even (or perhaps especially) the tough parts, is an essential part of your becoming Godlike.
And that leads us to our next point. I'm not sure I've heard prophets say that heaven is exactly all "happy" or "good." Rather, we are promised joy
, which is a much trickier business. People hear joy and assume total bliss. And that's a part of it. But joy is a very complex, intricate thing.
We are, indeed, promised a fulness of joy, just as Heavenly Father and Jesus Christ possess (3 Nephi 28:10
). Yet in the scriptures we also are shown multiple scenes of apparent non-happiness on God's part. One of these is in Moses 7
, perhaps one of the most touching passages in scripture. Here, in vision, Enoch sees the Lord weep. He's just as perplexed as you are: "And Enoch said unto the Lord: How is it that thou canst weep, seeing thou art holy, and from all eternity to all eternity?" If God is perfect, why is he sad?
32 The Lord said unto Enoch: Behold these thy brethren; they are the workmanship of mine own hands, and I gave unto them their knowledge, in the day I created them; and in the Garden of Eden, gave I unto man his agency;
33 And unto thy brethren have I said, and also given commandment, that they should love one another, and that they should choose me, their Father; but behold, they are without affection, and they hate their own blood;
34 And the fire of mine indignation is kindled against them; and in my hot displeasure will I send in the floods upon them, for my fierce anger is kindled against them.
35 Behold, I am God; Man of Holiness is my name; Man of Counsel is my name; and Endless and Eternal is my name, also.
36 Wherefore, I can stretch forth mine hands and hold all the creations which I have made; and mine eye can pierce them also, and among all the workmanship of mine hands there has not been so great wickedness as among thy brethren.
37 But behold, their sins shall be upon the heads of their fathers; Satan shall be their father, and misery shall be their doom; and the whole heavens shall weep over them, even all the workmanship of mine hands; wherefore should not the heavens weep, seeing these shall suffer?
God weeps because of the wickedness of His children, and the fact that because of this wickedness, he will very possibly lose some of them forever. I love this scripture for how much it shows God's care and concern over us. To paraphrase the last sentence, why should a father not weep over seeing his children suffer?
Now, back to joy. God has a fullness of joy, yet he also displays other emotions. It is my opinion that joy is more of a state of being than an emotion. It is not an absence of other, negative feelings, but seems to me to be a gigantic bundle of all knowledge, power, love, and grace while still maintaining a real view on the world. God knows the end from the beginning, and I imagine that there is great comfort in His infinite knowledge. Yet he also sees and feels the loss of his children. Perhaps joy is related to knowing everything will work out, who knows? Whatever it is, Joy is not a static experience.
I wish I could more adequately express my views on the matter. It feels like it's right on the tip of my tongue, but the topic is also probably too much for words to describe. One thing that helped me gain some perspective and which came to mind when I read this question is this segment
of Orson Scott Card's Shadow of the Hegemon
. Read through to page 187. Plus, Orson Scott Card is a Mormon, so I don't think the application here is meant to be a stretch.
In any case, back to the original question. To me, heaven sounds like an awesome place. Compared to this life, especially, it will be wonderful. I don't worry about it getting bland, boring, or flat-lining in the happiness department, because just as every child of God's adds to his glory, so will we also have the opportunity to have eternal progression, increase, and joy. And that is what life is really all about.