Not in the selective way you want. You can hide your profile from everyone, or have it visible to everyone. Fetlife has an option for having writings/pics visible to friends only, but not collarme.
You can hide your profile on the edit profile...but that hides it from everyone.You can hide anothers profile and block someone from talking to you by using the hide and block buttons on that person's profile.But other than that,I am not sure of any way to hide from a single person.You can just set it so you don't see them looking and they can't message you.
I would never use the collarme journal as a true journal for private feelings. When I was in Florida and went to a lot of concerts I put those in my CM journal. Men found this to be a good conversation starter. Think of your journal as part of your advertisement.
You can hide your profile from everyone or have it viable to everyone, my advice would be to have a profile that you would not mind everyone seeing, just be a bit selective on what you write there, or if that to make you comfortable just have a blank profile.