I like your post, as it exhibits a sentiment I can relate to (though I have had a FAR smoother existence than what you've experienced, thus far, I think). I hope you have a rewarding future and I hope that luck is on your side with that upcoming risky surgery.

To me, optimism is a form of acceptance of whatever may come. I will deal with whatever comes my way, and in the meantime, I will expect and work towards "the best" outcomes. Assuming/expecting the worst just adds friction and stress to my consciousness which serves no practical purpose. Why experience the bad things before they even happen? I face stressful "could go either way" situations with the mentality that it will work out, but I am fully ready to deal with the situation going as badly as it could. I prepare mentally for the bad outcomes, but don't dwell on it like many people seem to. It's just not worth it. I figured this out as a kid and developed that way of thinking throughout my life, refining and reinforcing it over time.

I've now outlived a number of friends who I just assumed would always be there to talk to. They died totally unexpectedly, heart attacks and stuff like that. The journey could be over at any moment. I recognize and accept the temporality of everyone in my life including myself, and I actually use this acknowledgement to motivate myself to embrace the opportunity of life and not waste time on stupid bullshit, including thinking negatively or dwelling on fear-based lines of thought. It's like a basic judgment I apply to almost everything I think about, just passively, and it's a great filter to optimize for spending time on things that I think enrich my life (or future life) and that of those around me who I care about.