I think it's quite common to feel sad and anxious after a cancer diagnosis and feel the future looks grim.
I think in quite a lot of cases it does mean your old carefree life may be over and there will be a tough time of treatment which can be an emotional rollercoaster, esp chemo, before you get back to a new normal.
I finished in Aug 22 found the whole treatment year a rollercoaster emotionally, got very low and very anxious but now I feel there's quite a lot to look forward to. During treatment distraction helped, Below Deck, or similar, days out even once a month can make a huge difference and pick you up, for me that was seeing puffins around the UK though that is seasonal but this time of year I did Edinburgh, horrific weather but seeing castle, Forth Bridge helped. Counselling may help, Macmillan have some via Bupa. Charity SomethingTolookforwardto online provides days out etc. Around now maybe fireworks, Christmas things, steam trains, whatever appeals. Then exercise helps, 20 mins a time for it to have positive effect or longer.
If can afford it get a cleaner in or any help you need. Some people find plants and gardening help, not me really.
Year after was tough for me as son in hospital 8 months of it but been to Maldives, Mauritius, Azores, Porto and France and done new kitchen, painting outside of house, new flooring. Financially Macmillan can help with advice. And I swim about 3 miles a week. Saw daughter get 12 almost perfect grades at GCSE, start A levels, get first job, turned 50, seeing her apply for university, get a boyfriend, there's masses of life left for you yet.