If fear of rejection has led you to distance yourself from people, especially groups, there are several specific things you can do.
First and foremost, you need to build a sense of your own self-worth.
In addition to this, cognitive-behavioral therapy offers three specific types of interventions…
From article Do You Want To Overcome Your Social Phobia?, by Bertil Hjert.
Image from book: Cognitive Behavioral Therapy for Social Anxiety Disorder.