Is my demotion unjust?

I work at a job in which it is only one person on the clock at a time. (I've been here for a little over a month now.) I had a terrible nose bleed that caused me to almost pass out. I called my manager who lives on site. It scared him to the point of asking me to take a different job which cuts my hours. He was weary hiring me in the first place due to my age. He told me that he has cousins my age and he would never make them work the shift I do now. (I am almost 20)But it's the shift I chose. I love my job as is and I apply myself. I've never had any complaints before and I go over and beyond to help out. Not to mention I'm here on time everyday and I do not drive and live decently far. My age has nothing to do with my work ethic. We do not have any sort of benefits here and I am fine with that. Age wasn't his main reasoning for the demotion. I'm not fine with getting my position taken from me in fear of my health and safety. I know my body and I know what I am capable of. A nose bleed could have happened to anyone at any age. Accidents happen. I have anxiety, but I deal with it effectively and I've never let something like that get in the way of my job so I don't understand how it is right that I lose my hours and pay over one incident? I told him that I understand that it's not only his family's business he's looking out for but my health and safety as well but shouldn't I also have a choice? I asked if I could keep with this position for a little longer to keep testing it out and he replied with it's best not, that he needs help with this other position anyway. I'm not upset, but at the same time I'm heartbroken because I love this job and I finally get things budgeted then the rug is ripped from under me? Help me please?