I poured my heart out straight away with my first therapist (even in the initial email before I met him) and as a result I was vulnerable and ultimately hurt.
With my second therapist I was cautious from day one and it's taken over 2.5 years to get to the point I am at now (there's not much I wouldn't tell him). He recently commented that it was important for me to try out being cautious when I met him and he was right. I didn't want to be hurt again. He has earned my trust.