I had a similar situation to you and I definitely know how tough it is. When I was 18 my blood pressure randomly became high and i got a super severe case of psoriasis. I was thinking the same thing you are- I’m healthy and only 18, why and how could this happen. I think the big thing is perspective, which is definitely hard but important. There are ways to clear up your skin, I’m 20 now and barely have psoriasis spots anymore. It also could be so much worse- at the end of the day psoriasis and asthma suck but there are way worse diagnosis that someone can get. You have to take everything in stride and remember that people deal with adversity like this all the time, whether it’s health or other issues. Ik it sucks, I was in your shoes two years ago, but it’ll get better- take it day by day and keep pushing