If you grew up speaking English, you have no idea how complicated it is for people who didn’t.
I have it. I had it. I did have it. I was having it. I have had it. I had had it, but then I got over it. On and on it goes.
But it isn’t just complicated for non-English speakers. We complicate our own writing by wading into this swamp.
Avoid the swamp. Avoid, if at all possible, anything that involves the verb have.
One sad example: see above. The author is telling a story, then wants to jump back in time. So she starts a new paragraph by saying, “He’d wanted to be a writer.” From this moment, we know that we’ve gone back in time — so from this moment, the author can switch to simple past tense: He wrote his first book … He reckoned with race as a boy … He made himself a stand-in, etc.
By sticking with he’d, time and time again, the author makes the writing sticky, forcing the reader to do more brainwork than necessary.
Search your first draft for the devil have and all its demon forms: had, has, ’s, ’d. If you can’t kill them all, trying letting the first one live and killing all the rest.