Trust issues...?

Part of me is totally okay with this situation. I'm happy with it, for that matter. Seems perfect.
Buuuut then there's that nagging feeling that I'm completely wrong. That my head's getting messed with again and that I should get over it once and for all. That I'm just going to get hurt.
It's easy to make decisions when you know the truth... but when you don't know what the truth is, it's harder.

I'm trying to decide if I would be making a wise decision by being extra careful, even if it might be hard, or if I'm just having issues because I know how this person used to act. I don't know if things are different now, or if this is one of those things that never change.

It's like I want to be forgiving, but at the same time I'm scared to death it'll backfire. I want to trust this person, and I kind of do, but something won't let me.

Something is telling me that this isn't going to end well... that I'm just going to get my heart ripped out of my chest and ground into the dirt.
But then there's this feeling that this will be totally okay... that if I just trust God, everything will work out.
There's also a small feeling that it doesn't matter what happens, I'll get over it eventually, and to just not worry about it... but I think that's just the reckless side of me :P

What do you do...
When you normally would listen to your heart and ignore what's in your head --my head's totally crazy anyway :P-- and just follow your heart because you know usually what you feel in your heart is truth... but then you get in a situation where your head is telling you to do something that seems safer than what your heart seems to be saying, and you're afraid to throw out the idea in your head because it seems like a better choice? When you're afraid that any feelings that may exist have finally hijacked your heart instead of your head just to confuse you?

I don't know if I'm supposed to just do what's safe, or to step out on a ledge, knowing God will catch me no matter what. I'm not afraid of what may happen... I'm willing to give it a chance. But at the same time I'm afraid of pain and I want to do what's safe.
I don't know if it's fear or common sense keeping me from trusting this person. I want to, but I'm afraid to at the same time.