I'm a little different than most people that want to be a vet, in that I didn't come to the decision early in life. I had considered it when I was in high school, but then proceeded to change my mind quite a few times before I met the research beagles that convinced me that I wanted to be a vet.
I worry that someday I won't be able to deal with those tough decisions and the guilt that's associated with them, but I'll have to find a way, since this is what I want to do with my life, regardless. As I've heard, it'll never get easier to euthanize a saveable animal and the day that it does is the day you should quit.
I just wanted to mention a few ways that other vets have dealt with the issue of euthanizing saveable animals.
I watched a presentation at school about 'doing well while doing good'. Basically, the premise was that you can make a lot of money by doing good things. There are vets that work in the intercity, providing low cost veterinary care to a huge number of animals that aren't often seen by vets. I think the guy was bringing in millions of dollars and, no, he doesn't have to turn people away due to their lack of funds (he's got a non-profit organization set up that helps fund this). It's not like he's not providing good veterinary care either; they perform complex surgical procedures and the whole nine yards. Now this isn't common, but if you were willing to look for something like this, you can do good for a huge number of animals. Or you can do it in your spare time to re-coop from the crappy things you might have to do at work. Just something to think about.
Other vets volunteer in their spare time, to prevent burn out. There are a lot of vets that work with rescue groups/humane societies, providing the veterinary care for free.
Either way, perhaps talking to vets or doctors about how often emotionally draining situations come up, and how they deal with them. Perhaps you could discuss the instance of the duck with the person responsible for making the decision.
