[Read: How to Claim the Love of Your Life.]
4. Know when to walk away. First, you've got to express what's bothering you to make your friend aware of the problem and see if it can be resolved. "We're all in our own movie. We don't always know how what we're doing is coming off to the other person," he says. "Once you've made the effort to work through the issue with the friend, and if they either deny the problem or aren't wiling to do the work and it's something that causes you real discomfort or pain, that's time to move on."
5. Be willing to be vulnerable. Any deep relationship with another human being will elicit challenges for both people. And that's a good thing – it's what creates intimacy and personal growth, Matousek says. And remember, true friends are the ones who like you for who you are, blemishes and all. "Once you let somebody in emotionally, you're going to feel their limitations. You're going to feel whatever their issues are." But at the same time, "friends can be a very safe context to work on personal issues, when sex isn't in the picture," he says. "To be able to be vulnerable with the people in your life is a huge gift."
[See: 10 Tips to Lighten Up and Laugh.]