As the states of the inner levels of angels’ love and wisdom change, so too do the states of the various things that surround them and are visible to their eyes; for the things that surround angels are given their appearance according to the things that are within them. We will describe what these are and what they are like in later chapters, where we discuss representations and appearances in heaven. Each individual angel undergoes and passes through changes of state like this, and so too does each community collectively. Still, one individual does so differently from another because people vary in love and wisdom. There are people in the middle, in a more perfect state than those who are around them all the way to the borders (see above, sections 23  and 128). But it would take too long to recount the differences, since the quality of love and faith determines how each individual undergoes the changes. Consequently, one may be in clarity and delight when another is in dimness and discomfort, even at the same time, within the same community. It happens differently in one community than in another, too, and in communities of the heavenly kingdom differently than in communities of the spiritual kingdom.
Broadly speaking, the differences in their changes of state are like the variations of states of days in one climate and another on earth. There it is morning for some people while it is evening for others, and some have warmth while others are cold, and vice versa.
I have been told from heaven why changes of state like this occur. Angels have said that there are many reasons. First, the delight of life and of heaven that angels enjoy because of the love and wisdom given them by the Lord would gradually pall if they were constantly engaged in it, the way it happens for people who are involved in pleasures and enjoyments without variety. A second reason is that angels have a sense of self or self-image just as we do, and this involves loving themselves. All the people in heaven are kept free of their sense of self, and to the extent that the Lord does keep them free, they enjoy love and wisdom. To the extent that they are not kept free, however, they are caught up in love for themselves; and since all of them do love that sense of self and carry it with them,c these changes of state or successive alternations do occur. A third reason is that they are made more perfect in this way, since they become accustomed to being kept in love for the Lord and kept free from love for themselves. Further, by these alternations of delight and discomfort, their perception of and sensitivity to what is good become more and more delicate.
They have gone on to say that the Lord does not produce these changes of their states, since the Lord as the sun is always flowing in with warmth and light, that is, with love and wisdom. Rather, they themselves are the cause, since they love their sense of self and this is constantly misleading them. They illustrate this by comparison with our world’s sun, which is not the cause of the changes of warmth and cold and of light and darkness, of distinct years and distinct days, because it stays motionless. The reason can be traced to our earth.
from Heaven and Hell, Sections 156-158