Hi Claire,
Well done for volunteering. I know it's really hard but as you do more, you devlop a routine and technique. This helps loads in taking away the stress and unfamiliarity of the procedure particularly when you're on your own with an owner as a new grad. Euthanasias used to fill me with dread when I first started practice (partly because I'd never done an equine one in uni and I've always been an equine vet!) as you want everything to go smoothly for the animal and owner. There will be ones that won't go smoothly but there's often a good reason - neurological deficits, low blood pressure, high adrenaline levels etc..
Although it seems morbid, try and volunteer to do as many as possible. Clients seem to judge vets on how they handle euthanasia cases more than anything. I used to get more thank you cards for euthanasias than any other consultations.
Hope eveything else is going well x