Hi Fred, I had 6 cycles of docetaxl followed by 6 weeks or radiotherapy from Jan to June 2015, during that time mentally I was ok but a bit less fit ( my running times were 25% slower for a marathon( yes I was fit before but nothing special and was 50). The area I suffered with was the sadness that you talk about. I got that from July to November , I think it was a bit about lots of attention and tests and positivity about doing something then nothing. I found it very hard, I could not face work and found myself bottling up the emotion when others were around. I used to and still do on occasions cry plenty when in bed during the small hours.
It has got better, I live for every morning when I can get up and go for my therapeutic run, then the world is better. I appreciate that I am lucky that I can run but my advice to anyone would be find the thing that does it for you and do it. My way of overcoming the lows is always always plan your " fun" for the next day today, then when you wake you know what you are looking forward to and after that plan the next day's etc. Works for me anyway, it may for you?