My job :(

This is my 4th week at my  job. I still can't believe I actually have it. But now, the true matter of the job is beginning to sink in. I was supposed to be there to see a dog getting put to sleep last night on my late night shift, but I just couldn't do it, I couldn't face it, I knew it would be horrible and I managed to get out of it by just telling the woman that I wasn't feeling up to it just yet. She wasn't long in telling me that I am going to just have to get on with it if I want my job. I know deep down that this is the truth but I just thought she might have been a bit more sympathetic about it. Guess not. I am to hold the next animal :( I don't know how the hell I will be able to bring myself to do it. I know it is part of the job and that you have to hold yourself together for the sake of any family's who might be there when the animal is getting put to sleep etc etc but its so much easier said than done!  I have always dreamed of being a vet nurse but I never really thought much about this part of the job and it is a major part. I guess you just  don't know when an animal is going to have to be put to sleep. I feel its different if the animal is old and is suffering but when it happens to a young animal it is so hard to accept.  THe dog that got put down was under a year old. It did bite someone's daughter. But, it was such a friendly dog, or so it seemed, it was so young, I just can't help thinking why did it bite the daughter was she teasing her??? I just don't see how a dog would just turn around and bite someone out of the blue for completely no reason. I mean I am aware that some dogs are just viscious buggars but on the otherhand sometimes it is the owners to blame for bringing them up in the wrong way. Sometimes it can be an accident too, a horrible accident that the dog turns round and bites someone and therefore has to be put down but still, its horrible, its not ever going to be easy.  I don't see me ever being able to do it :( How can I hold myself together for  everyone else if I can't do it for myself. I feel really down thinking about it right now. I even thought of giving up the job because I honestly don't see me being able to do this, I really don't :( its not something I want to do, but I want my job, but I really don't know now :(