My sister saw me cutting, how can I explain myself to her without having her think I'm crazy?

You could try to make her understand that it's not all crazy. Talk to her about how you feel and why you express yourself in cutting yourself. If it's maybe that you want to feel something or what the reason are to hurting yourself and she maybe won't understand right away but try to be calm and try to explain why you feel how you do and what it feels like, and then she maybe will understand a bit more.

Try explaining to her what makes you want to cut. If she understands she may be able to help you throught that problem

First, I hope you find someone you trust to talk to, and maybe find a better outlet than cutting. Explain why you feel the need, and explain how it makes you feel. I hope she is understanding and helps you.

Watching someone we care about harming themselves is worrying and alarming. If you feel able to explain what self harm gives you - why you do it. Let them know you are keeping yourself as safe as you can and that perhaps they can help you find healthier ways of coping or be there to support you when you feel the urge to cut.

Your sister caught you cutting and to explain to her without her thinking your crazy say something like "we are all crazy there is so such thing as a normal person. I am sorry that you had to witness this. I know this isn't the right way to deal with [depression, anxiety etc] and I would appreciate your support. "There are no secrets that time does not reveal" so never hind anything. If there's an issue that you want to over come ask for help.

Tell her there's a lot on your mind and you really can't find any other way to take care of these problems. Tell her you understand she might be upset with you and think you're crazy, but there's a reason you're doing this, you just don't feel ready to share it with her.

Talking to her about what has been troubling you would be a start... Self harm takes place becasue you usually need an escape from the emotional pain, and physical pain does that. The physical pain from self harming doesnt take away from the emotional pain, but it puts it on a back burner while you focus on the physical pain, and physical pain in easier to deal with than emotional. That doesnt mean that you should be self harming... Talk to your sister and tell her whats bothereing you. She is there for you and just wants to help you

Talk to her, explain what is happening in your life and what makes you do that, just talk to her and trust her at the end of the day she's your sister

Be honest, she might be freaked out and worried. But it's not an everyday thing people expect too see. Also try to stop, if not for you then for her, would you want too see her go down that road. It's one that hurts a lot, and ends up doing a lot of damage, mentally and phyically.