I sat in running car in closed garage for 40 minutes. feel completely fine but anxious about carbon monoxide death or damage, should i be worried? terrified?

The reason that you were in the car while running is of concern. Please speak to your PCP. If you have any shortness of breath, sleepiness, see the Emergency room.

I, too, am concerned about your circumstances. Were you considering harming yourself with carbon monoxide, and changed your mind? Discuss this whole affair with your doctor. Consider seeing a counselor.

The most common symptom of CO poisoning is headache. You didn't say how long it's been since your exposure but if you've been 2-3 days without symptoms, I wouldn't give it another thought...except I'd be VERY careful in the future about sitting in running cars in enclosed garages!