When did you know it was time to leave your field?

I have been in the dental field for 15 years and I don’t know if I can deal with insurance companies denying claims and patients getting mad at me because of that. I am ready to throw in the towel. I am currently an office manager, and I have a team that heavily relies on me. Lately, I just am questioning the idea of doing this until I retire. I have a food truck i’m currently working on but it’s still not ready. I think i’m scared of having the extra income of security.