I think it helps to know that it's impossible to know the future or what's in someone else's head. You can obsess about it, freak out, but it's not going to make a difference.
Ok, you start with the facts.

The it becomes what is your strategy for dealing with uncertainty. There are number of options ... you can decide you're not going to invest a lot personally until you get a better picture. Decide to just take it one day at a time to see what happens.
It's safe to assume that the other person is just another human being with his/her own problems, assets, strengths, weaknesses. And know that we ALL feel insecure to one degree or another.

And, that no matter what happens, you'll be fine.