I’m finally cancer free— why do I still feel sad?

After being diagnosed with PTC and having a TT, my doctor told me that everything looks good and now I will just need to monitor my levels with my endo and go for a scan in six months. All of my friends and family are so happy, but for some reason I feel the same. Sure, my cancer is gone, and that’s good, but my thyroid is gone now too and I’ll never get it back. I’m going to be on medication the rest of my life and constantly monitoring for any reoccurrence, so being cancer free doesn’t feel like much of a win. I know that probably sounds stupid, and I’m very grateful for my life and my good health, especially knowing many people diagnosed with cancer do not have as good of a prognosis, but I can’t help but feel like the cancer took so much from me and even though it’s gone, my life has been permanently changed. I know taking a pill every day is a small price to pay, but I still feel kinda defeated.