Here is a list of things that Peres didn't think were going to happen:
1. He believed the separation between the West Bank and Gaza would make things easier not harder.
2. He did not imagine that we would leave Gaza and they would fire Qassams from there.
3. He did not imagine that Hamas would show so strongly in the elections.
(taken from here)
In other words on some of the most important issues of the past decade he was absolutely wrong. The thing is he is not embarrassed at all for being wrong on every single one of these. It isn't just Peres, everyone on the left made the same mistakes. The problem is that they don't learn from their mistakes rather they repeat them over and over again.