When you are sleeping, you are non-resistant and all those experiences are joyful.

However, the dream doesn't occur during those times. The dream occurs in the few moments before awakening when those experiences are filtered through your physical self. Even a dream that seems to last several hours still occurs in the few moments before waking up...time is an illusion of the physical plane only.

It is that interpretation (through the physical self) of those joyful experiences that you perceive as the dream, not the actuality of the non-resistant sleep experience itself.

Because your (physical) vibration stays where you last left it, the vibration you had as you fell asleep is the one through which the re-interpretation happens when you re-awaken.

To try to make this concrete and understandable, imagine going to a movie theater...

The "You" in the following example is just meant to be a general person, not specifically You :)

As you go into the theater, you might be miserable thinking about all the major problems and worries in your life.

But as you settle down in your comfortable seat in the darkness, the film starts to roll, and the giant colorful on-screen images in front of you dominate your attention, you may find that your mood quickly changes and you soon forget about your problems.

Now let's say that the movie that you are watching was created to feel joyful and uplifting to the audience (representative of your actual connection to Source).

During the actual watching of the movie, if it is well made, you might now genuinely begin feeling joyful and uplifted. The experiences that the movie takes you through might make you smile, laugh, and just generally leave you in an extremely good-feeling place.

You are truly in another (joyful) reality during a movie like that.

But now, as the movie ends and the lights come back up, you remember again that it was just a movie. You watch the credits start to roll, feel a slight tinge of disappointment that the experience is over, and get up out of your seat and leave the theater.

As you head back out into the "real world", you suddenly feel the "shock" of remembering all your major problems and worries again and it's not long before you are back to feeling miserable again.

You realize that the magic of the movie experience is now gone.

To an outsider looking at your behavior, you were miserable before entering the theater and, soon after emerging from the theater, you were miserable again. So their natural conclusion would probably be that the movie was a miserable one :)

But the truth is that it was simply your perceptual filter that caused (and causes) your misery, not the joyful uplifting movie itself.

No analogy is perfect and this one isn't either. There are movies that we can watch that can genuinely change our outlook on our lives and leave us (for a long time, at least) in an uplifted and joyful state.

But in the world of dreams, this cannot happen...your joyful, uplifting, non-resistant experiences cannot override your physical vibration. So the non-resistant experiences that happened during the sleep state are immediately forgotten on waking up again, and the "filter" of our physical self dominates.

For more information, see If dreams are downloaded to our "consciousness" the moment we awake, why do we wake up from bad dreams? and the links within those related answers.