All is well. Nothing is lost.

[anagogy]

I am Ra. We leave you in appreciation of the circumstances of the great illusion in which you now choose to play the pipe and timbrel and move in rhythm. We are also players upon a stage. The stage changes. The acts ring down. The lights come up once again. And throughout the grand illusion and the following and the following there is the undergirding majesty of the One Infinite Creator. All is well. Nothing is lost. Go forth rejoicing in the love and the light, the peace and the power of the One Infinite Creator. I am Ra. Adonai.

i am curious,why do they say so??

They mean no "thing" is lost.

Perhaps these quotes will help you grasp what they intended to convey:

"63.8 Questioner: From last session, I would like to continue with a few questions about the fact that in fourth density red, orange, and green energies will be activated; yellow, blue, etc. being in potentiation. Right now, you say we have green energies activated. They have been activated for the last 45 years. I am wondering about the transition through this period so that the green is totally activated and the yellow is in potentiation. What will we lose as the yellow goes from activation into potentiation, and what will we gain as the green comes into total activation, and what is that process?

Ra: I am Ra. It is misleading to speak of gains and losses when dealing with the subject of the cycle’s ending and the green-ray cycle beginning upon your sphere. It is to be kept in the forefront of the faculties of intelligence that there is one creation in which there is no loss. There are progressive cycles for experiential use by entities. [...]"

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6.7 [...] Ra: "The dissolution into nothingness is the dissolution into unity, for there is no nothingness." [...]

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82.10 Questioner: Why does this partaking in the original thought have a gradient radially outward? That’s the way I understand your statement.

Ra: I am Ra. This is the plan of the One Infinite Creator. The One Original Thought is the harvest of all previous, if you would use this term, experience of the Creator by the Creator. As It decides to know Itself It generates Itself into that plenum, full of the glory and the power of the One Infinite Creator which is manifested to your perceptions as space or outer space. Each generation of this knowing begets a knowing which has the capacity, through free will, to choose methods of knowing Itself. Therefore, gradually, step by step, the Creator becomes that which may know Itself, and the portions of the Creator partake less purely in the power of the original word or thought. This is for the purpose of refinement of the one original thought. The Creator does not properly create as much as It experiences Itself.

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So what we think of as "creation" is not "creating something out of nothing" but rather, the creator simply plumbing the depths of its own substance. That substance has always existed, and always will. Hence there is no loss.

It had no beginning, so it can have no end. The creator is uncreated, and eternal.

All is well.