Time.
No one said you had to be vulnerable from the start.
When you begin a friendship, you can do so with plenty of caution and distance. Just because you made a friend doesn't mean you HAVE to expose your fleshy underbelly right off the bat. Take the time to get to know your friend; learn about them, learn who they are, who they've been, who they want to be. Find out what made them who they are today. Find out where they are in their walk with Christ. You can do all these things without giving away intimate details about yourself that would leave you vulnerable. Test everything, listen to the Spirit, and only give what you're willing to give. You're not bound by some unspoken oath to bare every facet of your soul to a brother or sister in Christ.
I'm sure that many people here in Singles think I'm an open book, because I share very willingly. ("I mean...you guys all call me Fat Amy...") But one of you knows quite well that I'm far, far more withholding than I seem. ("...and my real name is Fat Patricia.")