I work for a boss/project manager at a new company who is a total 180 from my former boss (which is why I picked him) and creates a completely different culture in the project team. He is very optimistic, and assumes that people want to do their best work until proven otherwise. If the work is slow, he tries to figure out what the reason is and address the reason, instead of getting more aggressive. He makes decisions based on what the pros and cons of his decision will be, and by thinking through what he wants to achieve. I like my boss very much, and have never respected someone I work for as much as I respect him. Besides being a very considerate and appropriate manager, he's a nice person who likes to have some kind of relationship with the people he works with, person to person.
However, because of past experiences at my previous job, I feel very anxious at work, and am oftentimes withdrawn from my boss and co-workers. While I like my boss and most of my co-workers very much as people, I am afraid to open up to them. I know my boss would like me to trust him more, and I know intellectually that he has given me every reason to trust him, but I am afraid to. I also oftentimes experience overwhelming stress, anxiety, and fear at work in which I am suddenly terrified of getting fired, and begin looking around for a threat, or something I could be in trouble for. This fear interferes with my work and slows down my progress.
I believe I am a valuable member of the team but am having trouble fully integrating.
How can I better adapt to the culture of my new team?