As Muslims we believe that God created us all for a purpose. An animal too has its purpose. Honestly the goat I saw being slaughtered seemed far more calmer than what a human being,God forbid, would be like when faced with the same fate. This is because we are all created differently.
I eat meat and fish. And I am aware that they were all once living and had to be killed to be consumed by us. But we as Muslims believe these animals are already aware of their future.
I am an overly sensitive person..very. So honestly be it a goat, a chicken, or even a fish I need to constantly remind myself that this was why God created them. That they will be of sustenance to another. Just like He created me for a purpose too. As humans we may go through many hardships and suffer much pains too. Its all a part of our mortal existence. And God is not unjust to anyone. Though it may appear otherwise to us, no one will ever suffer in vain.
That said one needs to bare in mind that killing an animal,for any purpose, has to be done devoid of torture and oppression. You must make sure their deaths are as instant as possible.Also you cannot kill for pleasure but sustenance or absolute necessity (like say you kill an animal that is dangerous and may cause you harm)
I hope I haven't offended anyone. bare in mind my faith is different from yours. My ideas and feelings too are hence different.