The "fear" can be anything, including fear of simply living, mighty risky business. Call it what you will, living is not easy, not a trip of fun, excitement, thrills, etc. It's a struggle. For most everyone. These days this reality is suppressed, obfuscated.
What to do? A therapist may help, perhaps some meds, some talk therapy, an introduction to CBT and its aspects. Then it's up to you. Believe it or not, learning about yourself, learning to give to others, can be a great adventure of discovery. Give it a chance and share what you learn so we can all learn. That's the beauty of a site like this.