Personality can change that's why there are terms such as premorbid and postmorbid personality. However, this is more to with various pathology like OP described rather than a true intrinsic change and this pathological change is dependent on personality traits. Some people are just more sensitive to changes in life and get affected more. An identical event in 2 otherwise identical people, will not affect them the same.
I don't think adult personality itself fluctuates that much, sure someone may appear very different in terms of dress sense, hobbies, behaviour and meaning of life at some point in life, but the frame of his/her personality is still there like always. Just what was inside that frame has changed for now. Existing pathology can often get worse with age too like any illness.
There are various options for dealing with hair loss and succeeding somewhat, at a point we all find ways to deal with any adversity mentally and physically, that's how human nature is, even if you were one of the unlucky young aggressive sufferers. You'll somehow adapt even if you initially thought you couldn't. Norwood 7 can wear a wig or get transplants and keep it buzzed, life should almost be like before no? Sometimes I feel on here the problem is clearly not just hair but other more pressing issues and that's perfectly understandable. Some people I've seen even have a full head of hair/good looking but can't believe it or are worried about ageing. There's a myriad of general life worries, bdd or lack of a rewarding life due to autism or whatever. There's help in dealing with all this, that's the take home message and don't suffer in silence which just makes it worse.
My love for life will never diminish till the last breath, there's too much beauty out there but it depends on how you view it of course. I'm just as happy feeding strays as I am with my family, close friends, travelling or other hobbies. Personally I always believed in fate and I count my blessings because I got lucky with many things. I want to go out with a smile regardless of what may be thrown at me in the future. There are tons of inspirational people who went through hell but kept their composure, happiness and love for life intact yet I don't have their terrible experiences.
@disfiguredyoungman glad you're still here bro and I hope you get your happiness one day.
I'm sure much of what I wrote some may find utterly useless especially the ones who go on various autistic like forums, but this is my opinion and how I live my life. Happiness is as much of a choice as misery in many cases.