It's a nightmare. Wake me up.

[MrBond]

"I do recognise my part and I take full responsibility. But the A was her decision."

Yes it was.

"I can even understand her "falling in love". But should I just give up and say: "It is all my fault, that you fell in love"?"

No one said you need to give up.

"Is it not enough to blame myself for my part of this mess?"

Stop "blaming" yourself. That's all fine and good for a pity party but what you really need to do is to take action and change. Blaming doesn't do anyone any good.

"Should I also take the responsibility for the A?"

Of course not.

"We talk about 20yrs of living together and most of the yrs were good."

Again, that is a matter of opinion. You think that while your W may think otherwise. Don't mindread her. Just say that's how YOU felt.

"Am I so wrong when I think, that this should be dealt with more respect toward the partner?"

In an ideal world yes. But you need to understand WHY she's reading books like the ones she is. She's working through sheer emotion. That has no basis in logic.

"I am convinced, that the A is her main reason for breaking up."

I thought you said you read the books? The A was a result of all the built up resentment and issues from before. The A was just her lifeline to move on without risk.

"It was the wrong man at the wrong moment, meeting her needs for affection and romance."

Again, that's YOUR opinion which really doesn't matter right now. All that matter's is HER reasons for doing what she's doing. Do they make logical sense? Maybe not. But nonetheless that's what SHE believes. You can either continue to deny it and not get to know this new person or get a D and start over with someone else.