Having had cancer myself 5 times, I often thought of this, and even worse, but in retrospect 3 years later, I'm still here, and happy with that decision to go on, which I can't say was easy. Have you discussed this with your doctor, family? Maybe see a counsellor to get you though these tough times, and maybe some meds to make you feel better. Some of the effects of treatments are temporary, like taste, and will come back to some extent. Without completing treatment, you may not have time left to enjoy yourself. Hang in there, and reconsider.