It has hit me too. But suspiciously a few weeks after starting Tamoxifen...
I ended up having an emergency appointment with the psych onc at my centre because I found myself crying all day and with an overwhelming feeling of sadness. I felt so much better after crying in her office for an hour and telling her how much I hated this whole expereince and hate what it has done to me and what it means for my future life.
She got me in to see the centre's psychiatrist who listened to me and at the end of our time told me she felt that I was entitled to feel sad and angry. She didn't think I needed anti-depressants but regular meetings with the psych onc for a while.
Hope this helps in some way... Jenn