How many years of experience do you have?
I can completely understand how you feel. I have a few suggestions to reduce the anxiety a bit:
(1) Financially: Save as much money as possible every month. Keeping a fund with 8-12 months of runway will go a long way in reducing your anxiety.
(2) During Work: Try your best to keep learning and growing. Build context of your systems, go through that big file of code you're afraid of reading. Share this context with others and use it to solve issues or suggest improvements. Impress with your quality of work and try to be on good terms with your manager and coworkers.
(3) Outside Work: Keep some time aside every week to passively prepare for interviews - DSA, software design, system design etc. Keep your resume up to date and always ready to go. This will give you some confidence to be ready to crack an interview as and when required. Every 3-4 months, apply to a few places just to interview passively.
(4) Mentally: Adopt the philosophy of stoicism. Face your worst fears and try to think of ways to deal with them.
All the best!