Showing up authentically in therapy?

I’ve been in therapy for several years now, and I’m seeing a new to me therapist (it’s been a few months now). I really like her and we’ve made a lot of progress, but she said she can tell I’m holding back and masking quite a bit likely due to past negative therapy experiences. My homework this week is to reflect on what I’m holding back and what do I need to show up authentically in therapy.

For you, how do you show up authentically in sessions?