> I'm a heck of a lot more cautious in a group than I am one-on-one in a relationship with an easygoing (<- my only type!) partner.

Maybe... But then your issue isn't that you want to feel closer / more bonded to a partner, your issue is that you want to feel closer / more bonded to other people in the group.

> I know I need to take risks. It's the actual doing where I have a problem! Seems I'm hampered by fears or worse: the feeling that there's nothing I want there anyway. That feeling is worse than fear. Fear I think I could get past.

I guess there are two parts to the issue:

1) Knowing what is on your mind
2) Sharing what is on your mind

Sometimes my mind goes blank. I simply don't know what to say. I don't know what I'm thinking or how I'm feeling. I think part of that is a defense, however. Sometimes things occur to me and I do know what is on my mind. Then the issue becomes one of sharing what is on my mind.

Sharing what is on your mind (and having others connect with that) is a way of feeling accepted and cared about and bonded to other people.

When one shares one is indeed taking a risk. The risk is that others won't connect with what we are saying. That could result in our feeling isolated and misunderstood and incomprehensible.

Little risks...