We are social beings with habits. Our addictions go way beyond just substance. We are addicted to our surroundings, family members, behaviours, belongings, etc... In any type of addiction when the matter is taken away, we have a tough time coping with that. You see people being upset to lose a job. This is not always just because they loved the job, but it is partially due to the fact that they knew at this point what is expected of them and they had it down to a routine. When the routine changes, the habits and everything else around that must change. This brings about the suffering they go through due to this change.
When someone from the family transitions; with the same token, we have been used to that person being around for a long time and behave around hem a certain way or have certain expectations. We have memory with them and their transition brings about the thoughts of the fact that now there is a time and expectation value vacuum. The time you spent with this person becomes free time. The expectations you had from them and they from you, are no longer there and since this had become an addiction over the years, now what is supposed to replace it?
As time passes and the vacuum is filled again, only the memories remain and now the addiction has shifted. Those who have gone through many changes throughout their lives, seem to be able to cope and get over the transition issues much faster, as well as those who have been through some extraordinary circumstances like living through war or working in a graveyard shifts in the hospitals.
For the rest, we would need to understand the unity of the fact that there are no energy loss. The body is no longer visible to us, but the energy and signature remains forever.
Be the Light!