Something maybe not mentioned about cancer is that it puts you in situations where you're suddenly faced with an impending death or very uncertain future--no control--and survival instinct kicks in. You are put right in the bargaining phase--if I can just get better (and it has all these targets defined too), I can go back to living, and I'll treasure everything more. Patients often experience a 'post surgical high' for a multitude of reasons, partly because they realise they can experience whatever gave them joy and what they overcame was worse than their problems.
Of course, they often experience psychological problems too. It can be lonely—many patients don't actually have the kind of constant support described in this thread, though the support I've had during my surgeries is something I wish I could have for my depression—and bleak, full of setbacks and uncertainty and pain and isolation miserable drugs. What I mean by this is that even people who are fighting respond rationally to the shit things by feeling crushing pain, and ponder giving up.
Part of it is emotional survival instinct because they haven't the philosophical change from suicidality, part of it physical because they're suffering so much. The body drives you to heal. We survived as a species through that kind of resilience. When I invoke that, it's not to say that suicide isn't rational ever—I agree with Smilla. After all, resilience can be overwhelmed by stressors. Humans do have an astonishing capacity to adapt to fight for their lives though.
It happens to ideational people to some extent too. But depression and grief dampen it.
I fought like mad to get better from my brain tumours because I had hope and renewed perspective and didn't want to be ill—and then ended up going back to planning to kill myself when my sustained efforts to improve my life variously failed or were overwhelmed by my long term mental illnesses. I did recover from one thing, but my life had permanence that transcended my illness. That can work either way, and most people's lives are better than their illnesses.
I think people are wrong to dismiss you Shay. I think you are going through a profound and very natural grief over a loss of many things, including control. It can be hard for others to empathise with how central body image is--not just in our deepest understanding of self worth but others' and our conceptions of our selves, negative and positive. And it's fine to love something about yourself too and of course you will grieve and despair as it goes. What you're dealing with is something many (especially non-terminal) cancer patients find the hardest to deal with - hair loss and changes to the body. Having to live with that change even after 'getting better' is hard.
It would be very surprising if you could go through this painful process and endure with a smile, no matter how great your life is otherwise. Suffering is relative, but this is also a lot of suffering. It's possible you'll adapt over time, even in a limited way, with your support structures. I can't say. I think many women (and men) in your spot would feel hopeless—major life transitions of this kind do tend to induce depression as well as grief, and it's a terrible loss. So of course you feel... loss.
I'm sorry that this isn't more insightful. I hope that I was able to convey that your feelings are reasonable and expected, just like a cancer patient's determination and grief. You aren't responding in some weaker way that nullifies the value of what's around you, you're experiencing something that overwhelms your ability to connect to it.