Positive attitude

Hi @pinkhope,  what @Zoffiel said is right. It's normal. Actually what happens physically with surgery and treatment is that we pump out lots of adrenalin to get through it all and as they say what goes up must also come down. It is a natural process. The trick now is to get past the really down stuff. 

I agree seeing a counsellor can help. Mindfulness practice can help too. I walked every day and practiced mindfulness and meditation.  Sometimes I really had to push myself to get past the negative thinking. The thing is our minds play tricks on us and we need to control those thoughts.

Try not to stay or dwell on the negative. Gratitude rituals work too. There is a little app called  Delightful. It's easy and poses 3 questions to answer daily. Practising gratitude has been proven to change how the brain thinks. It changes the neural pathways in the brain. It worked for me and I use it every day. Could be worth a go for you too.

There are a couple of books that helped me, one was called Your Life Matters by Patrea King.

I hope you feel better soon. Best wishes