Many different chemos effect your hormones. Mine has caused me to go into chemopause (menopause caused by chemo). Because I am going through menopause, I have found myself to be much more emotional.
Going through the cancer journey is difficult and emotional. Even when I am not on chemo, I have many emotions. Sometimes I forget about everything and can be happy. Sometimes I am angry that this happened to me. Sometimes I am sad because of everything and I am just wiped of energy and can't take another step (physical or mental).
It's important to have an outlet for your emotions. They are very real and don't try to tuck them away. I keep a journal and write when I am feeling emotional and sometimes when I'm not. I never go back to read my entries. Just getting it out on paper helps so much.
I also see a psychologist periodically. I really think to beat cancer, it's not just the physical aspect but the emotional and mental aspect as well.
Good luck and don't be afraid of the tears!