There are many times in the life of an adopted person where the loss of adoption is stronger.
1. Birth - The loss of your mother at birth and subsequently any foster home you were placed in before adoption. You may not remember it, but your brain was wired with the loss.
2. The loss of growing up adopted. The lack of mirroring and fitting in. Even in the best of homes children face this loss.
3. The death of a grandparent. Realizing that you are not the descendant of that person and the rest of your cousins are.
4. The birth of a child. When adopted people have their own children it can be tremendously triggering. How could anyone give a baby away? When the child reaches the age that the adopted person was placed in their home they realize how much they would have missed their previous caretaker.
5. Biological family reunions. They can go well and the adopted person is sad on all the time they've missed out on. Or they can be rejected and the adopted person has to give up the fantasy that there is someone out there who loves them and wants them.
6. The death of a parent. When an adoptive parent dies it signifies the end of an adoption. Extended family may not continue the relationship with the adopted person.