I maintain by keeping a singular focus on our purpose.
ITA. Having my list of key points in front of me helps me do that too.
I think what you don't want is to go in feeling defensive-- they are calling the meeting because they are annoyed (about something), but you don't have to feel that you are up against the wall about that. Instead, you can turn it into a troubleshooting session framed in mutual terms:
--hear what they have issue with, and make notes
--but then make sure they know what YOU think is really going on, and give them evidence as needed to support your points
--ask them to solve what YOU think the actual problem is
--only after hearing their solutions, offer solutions that are acceptable to you; hopefully these can be offered as "tweaks" to their solutions, but if not, offer yours anyway.
You don't have to accept any solutions that are unacceptable to you. You can always ask to continue the meeting after gathering more data or information.
