Back in the 1970s First Aid was often taught in a somewhat negative manner. "If you do this or don't do that, you will kill them!" Many people shied away from helping - not good.
Then we moved to "Doing something is better than nothing!" This philosophy proved problematic as it lead to poor First Aid.
My teaching method today is to encourage people to help and to do the best they can under the circumstances. You are not expected to be perfect, just to do what you can to the best of your ability, training, and conditions.
If you are worried that the cost of an ambulance may be an issue to the patient, remember this: not your problem and the ambulance is cheaper than a funeral.
We need to take something positive from case studies of First Aid gone poorly. It is a basic First Aid tenet to call EMS for all medical emergencies, and remember that the patient is not always going to make rational decisions. The patient may have the right to refuse treatment but they can't stop us from calling for help. Our job is to recognize the emergency, and provide appropriate care, within our training scope, until EMS arrives.