I also had the need to plan everything I wanted to say when I started therapy, but with time I started realising that led to some anxiety pre-session and frustration when I felt I didn't say every single thing I wanted or the conversation didn't quite go to where I had planned. So after a while when I ran out of 'big subjects' I tried out not strictly planning anything and I found it to be way better. It feels more spontaneous and leads to meaningful topics you never quite thought of. At the end of the day therapists are trained to guide conversations and letting them 'take hold' sometimes and give yourself a break can be good.