If I Start to Feel Sick, Should I Receive Healing or Enforce the Fact That I’m Already Healed?

Either will work.  God is not nitpicky about matters like this.  It would be my personal preference to command whatever is causing the disagreeable feelings in the name of Jesus to leave (consistent with Mark 11:23) and declare that I am the healed, not the sick.  I would emphatically declare that I will not receive whatever the disease is.  We should identify as the healed, not as the sick, because that is how God sees us.

Many of us have learned the hard way that the best way to deal with sickness is to run it off at the first symptom.  If you wait, you’ll probably have to shift over to believing to be healed of whatever has taken hold in your body.  If I were looking to be healed of a condition that I’d had for a while, I would believe and receive my healing when I pray (Mark 11:24).  If it were a first symptom .I would enforce the fact that I am the healed, not the sick, and rebuke whatever it is so that I don’t receive the sickness.

See also:

Should I Believe That I Receive Healing or Command Sickness to Leave?