Why do other people yell at me for self-harming? Why can't they be more sympathetic?

People only tend to see the immediate danger of what you're doing and not why you're doing it. Just because they lack understanding it isn't out of lack of caring, just ignorance. Communicating with them could be a great way to help them understand a little more about what you're going through. Self-harming is obviously a very serious issue and can go wrong very quickly. It's always recommended that you speak to your doctor or a therapist, or anybody you may feel comfortable speaking to.

I think people yell at you because they do not understand why and sometimes it is because they care.

It’s a lot of information for them to take in at once, and that’s a hard topic to talk about. I know that you see it as them trying to bring you down, but try to look at it in their shoes. How would you react if you found something that big out? Do be so hard on them and don’t be so hard on yourself, it’ll get better. They want to see you get better even if it means them being a bit upset. Talk it out, just give it time. And remember you have what it takes to make it. This is just a hard test and you are going to pass it.

Sometimes it can be difficult for people who is close to us to deal with this information. It also triggers a variety of feelings and sensations in them. Ofcourse it is not the best reaction and it doesn't help you to get better, but it is normal that people doesn't always know how to react and sometimes feel incompetent and scared. Yelling at you can be a way for them to deal with the things they feel about it. You can try to talk in a deeper way about it, expressing that you need more empathy and sympathy from them, and acknowledging their feelings too.