Here’s an excerpt from this excellent article by a father who himself was adopted when he was 1 1/2 about what he and other kids who were adopted struggle with.
I was adopted when I was 1 ½ years old. There aren’t many relevant details to tell about the actual adoption right now apart from the fact that I know (now) my biological mom loved me but couldn’t keep me, and my adoptive parents acquired me (and my twin sister) and grew to love me. My life has been pretty good. I’m a normal-ish person. I have no major quirks, and I’m happy. However, hindsight makes trials appear less rigorous than they actually are; I might have turned out differently had not a few things gone my way. Of course, everybody has hurdles in life that they must overcome; it’s not like adopted kids have it tough while everybody else gets a free ride. But, it is true that adopted kids have special issues that most kids will never have to deal with. They have to resolve feelings that most other kids don’t, and that necessitates a different kind of parenting.