Michelle,
I am doing an art therapy class at the minute and our teacher is a t and she was crying at the start of our class last week so I asked her what was wrong and she said she had a really tough session before our class and sometimes she forgets how hard her proffession is. So in answer to your question they do think about their clients after hours and it does upset them sometimes which is why they are so good at self care and have lots of tools to help them deal with their own up's and downs.