There is a reason for this question, the person who wrote it knows to develop the Dhamma, to actually practice as a Buddhist today, you need certain conditions. If you are starving in the middle of Africa, you really can't do the Dhamma very much, you really need some food, that is all you want. So if you are in too much suffering, you actually can't practice that well. If you are too fortunate, too rich, too popular, too, you know, you only have to look at some of the music, movie industry people who get too caught up in their fame, they just love their money, etc., that is too much of the material happiness and they can't do the Dhamma practice well either. In order to practice the Dhamma it is important to have a balance of happiness and pain, Sukkha and Dukkha. To have a balance, that is good. We learn more, we have our happy times so that we are not worn out like the starving person in Africa, but we also have enough Dukkha that wakes us up and doesn't make us into a sleep kind of state, like the rich people who get lost with their money.
So the human realm is a good place for practice and you all have that good fortune. Now the reason this person asked the question is that according to the Buddhist theory of the heaven realms, they are all wonderful, all beautiful, all lovely. It is like you eat all the food that you want and you never get fat, you never get a pimple, you have a perfect body - handsome, beautiful, everything you want, celestial music, whatever, everything is beautiful. Those are the heaven realms Buddhism talks about, and it is not a good place for practicing the Dhamma. People get too caught up in their happiness. The pain that they have comes only in the last five minutes of their life.
Can you imagine having a lifespan of like 50,000 years of happiness, bliss, material comforts and everything, and then in the last five minutes you get everything going wrong. That is what they describe, everything goes wrong. The body starts to smell first. The reason why the body smells first is so that all your friends will run away from you, that way you die alone. There is no one in the heaven realms who dies with others around them, they all die alone because the smell is so terrible, it is the first time ever that people in that realm have smelt such a bad odour, so people run away. Then the aging process starts. You were born with a perfect body, about 25 years old and you stay that way all the time, yet then in the last five minutes when the smell starts, the body starts to decay quickly. Everything that happens to people from when they are 25 until they get to 80/90, all that decay, the wrinkles, all that grey hair, etc. happens. Think about that - in five minutes after you have had 50,000 years of bliss. It is horrific. They say that people in the heaven realms die of such horror and fear that it blanks their minds, that is why they can't remember in their next life.
Now, back to the question. Ok, the heaven realms are supposedly not a good place for practice, because there is too much happiness. So, this person wants to know, how they can avoid going up there and how they can actually get back to human birth so that they can practice again here. I don't have any guarantees on this. So don't get upset with me if you end up there after doing so much good. But a dedication is what I believe will help you. A dedication such as "For every day of my life and lives, may I be in contact with the true Buddha/Dhamma." That is something that I say regularly. I want to be in contact with the true Buddha/Dhamma. Hopefully that brings me back to the practice whether it is human, or maybe they do say that a few people in the heaven realms will wake up and they do actually practice. But it is hard for them because they are so isolated. So when I rededicate the dedication, it focuses my mind, "yes, I want to stay with the Dhamma." And probably that will be as a human again. So maybe if you make a dedication on a regular basis, it might produce benefit as a powerful karmic push to get reborn as a human or a possible heaven realm where you do have a bit of a chance for practice. But I have never actually read anything that will guarantee this.