It differs between people, but i find keeping myself away from people and situations that are emotionally exhausting (which is all of them when i feel like that) helps. Going somewhere like a river, or a wooded area - nature always reminds me of reasons to be alive, and it clears my head better than meditation ever could.
Taking the time to deal with your own feelings and issues and putting other peoples on hold for a while (sounds selfish, but you have to look after yourself before you can help others) - be honest with people if you cant deal with their dramas and issues at the mo.
Surround yourself with things that make you happy and make you feel safe - no matter how small and redundant these things feel now.
Talking helps some people, whether its with a loved one, someone that knows what you are going through, a stranger that is willing to listen (im sure all of us that have answered will be happy to exchange PM's if thats what you want - ive personally blurted things out to a random stranger that i wouldnt see again on more than one occasion - which helped), or a professional (i would very much suggest you have counselling as it sounds like the result of a specific trama).
If you self harm:
A rubber/elastic band worn on the wrist is a common method of helping you not to hurt yourself - as is holding an ice cube in your hand. Sounds lame in writing, but may give you those precious few minutes to think about what you are doing, and whether you really want to do it. This is only a very short term fix though.
Volunteer work may help boost self esteem if this is an issue - though i havent personally done this.
Know that you arent alone in this, and that there are many people that understand what you are going through - never think that your feelings and inability to cope is an overreaction or that you are not entilted to feel that way. We all deal with things differently, and sometimes we feel weak or need time to heal. This doesnt make you less worthy, or that you dont have a bright future - it just means that maybe its clouded right now, but this WILL change.