Yes, you can be too vulnerable with people. But only when you expect them to own your happiness. Only you can own your happiness. As long as you are the one at the wheel, I don’t feel you can be too vulnerable.
Relationships, in general, only work when two people like each other about the same amount. If you notice that the scale is tilted one way or the other, then no amount of vulnerability is going to fix that. Hope that helps?