sometimes it's hard to think IN the therapy session, so I have to respond with something like "I'll have to think about that some more." The I *might* be able to think more about it when I'm alone. or I might continue to not let myself thing about it. without meaning to, i do things that stop my thinking or distract me from thinking.
As my T says, you will remember when you remember. There isn't any time limit and it's okay. Trust the process.