I wouldn't think of it as a roller coaster. You don't have to roll back down again if you don't want to. Believe in your ability to stop it now! Right now, while you're feeling bad about having done it, try writing down all your reasons not to. Then the next time you feel like hurting yourself, you can refer to it. Can you think of some better ways to relieve stress? If you get the feeling you want to lash out a lot, could you hang a punching bag in your garage or basement? Do you have a friend or family member you could talk to about this, so you could call them when you're feeling bad?
Are you receiving treatment for your panic attacks? This is something that should be addressed. You shouldn't have to fight these alone. Can you contact a counselor, therapist, or doctor regarding the panic attacks and depression? If you are already in treatment, can you discuss this with your treatment provider? They can help you learn ways to avoid hurting yourself in the future.
Please take care. Thank you for sharing this.