Are there any jobs I really need to try to avoid?

Depends. If you are concerned about working and don't understand your fears, you should spend some time talking with a therapist.
Yes. Any job that aggravates a medical condition or would put you at risk due to your medical condition. This will of course vary depending upon your particular medical condition. For instance, asthmatics would not do well in jobs involving dust, fumes, extremes of temperatures and dander exposures.