Chinese languages

I'm a beginner in Chinese, so I'm sorry if this is a silly question - Is it acceptable to mix traditional and simplified hanzi together in the same sentence? Do all characters even have both a traditional and simplified version?

The following is a poem from Lisa See's book "Peony In Love". I know it's quite a depressing poem, but I've wanted to translate it into Chinese for a long time now. So far, nobody has wanted to help me with this. I only have very basic Chinese skills, but I tried the best I could at transl...