Regarding what the American female doctor said to you --
For various maladies, with most of the doctors I've seen, they've mostly listened and examined and given advice/prescribed medicines, without telling me what they thought the outcome might be. Acting neither pessimistic nor optimistic, they gave no sign as to how they thought things would go. I'm sure they are trained in medical school to act that way, and their constant exposure to human ills and concerns must make them numb, and cautious.
However, I had a doctor a few years ago who, at the very end of an appointment (about a different medical condition, not cheilitis), looked me in the eyes and said to me with conviction, "It might take a while, but I know you will get better, and I believe things will work out in your life."
I could not believe how supportive that was, how positive that made me feel - to have her express her hope and belief that it would get better.
It makes a lot of sense that this type of attitude and behavior on the part of doctors would help medical patients (no matter what their problem is), of course.
Later, I read about some medical studies that had shown that if a doctor says optimistic things to the patient, or (which is fascinating!) merely holds the positive thought inside his/her head and doesn't tell the patient but still believes that there is hope and the patient will get better, the patient is more likely to get better. In other words, holding a belief that something good will happen with the patient's condition, especially if the doctor tells this to the patient, will result in a better outcome for the patient, statistically speaking (so, it doesn't work in every case, but looking at many cases together, doing this helps the patients' health more than not doing it).
In recent years, I have been an advisor and a specialized sort of consultant hired by people and businesses to guide them through a particular life/work situation, and after reading about those medical studies I described in the above paragraph, I made it a point at the end of our time together to actually tell the people I was advising that I thought that the situation they were going through would work out well for them (if I could honestly think that).
[For about 10% of them, I felt that the situation they were about to enter was going to be a disaster, and to them, I didn't lie and say I thought it would be a good experience, obviously. In those cases, I was delicately honest with them and tried to warn them calmly about steps they could take to make the situation more positive than it was looking like it would be for them.]
This research is also why I try to be positive to people here who seem despondent about their cheilitis. Also, it's why my name here is W.G.B. which stands for "will get better".
It's not pretend "positive thinking", slapping a fake happy face on a bad situation, but instead a sincere hope, and a kind of "prayer", that the situation will get better.
Martin Seligman, one of the major psychologists of the last 50 years, calls this "learned optimism". Originally in his career, Seligman was a pioneer who studied "learned helplessness" about people and animals who give up in their lives, and so their situation gets worse and worse, even though there were easy things for them to do in order to make their lives better, but they just didn't do them or pay attention to them. In about the last 12 years he's studied the opposite, how people can learn optimism and positive thinking, rather than learning negative thinking. It's not just mumbo-jumbo pop psychology, these are real, statistically and experimentally-proven phenomena that make a big difference to the way people's lives go.
Some folks on this forum are understandably negative about their cheilitis, and it has cast a pall on many other aspects of their lives. This is natural, and understandable.
And I think it's fine to choose to be negative about your own life - you have the freedom to do that. That might make you difficult and depressing to be around for friends and family who are close to you, but it's your choice.
But when people give negative comments about other people's lives and medical conditions, and pronounce a bad prognosis for the future, especially when they don't even know those people, I think it's unkind, illogical, and unacceptable. It is not up to any person to say to another person, "You will never get better, you should give up, there is no hope."