Just talk to yourself; catch yourself being unsure about something you've said/done and be on "your side" by telling yourself it will be okay, that "You" are there with you. Or stand up for yourself when you put yourself down. If I call myself an "idiot" I've trained myself to automatically answer, "I'm not an idiot!" :-)

Make yourself laugh/relax. Tell yourself you're going to strap your clock to your wrist and imagine that, so you can take it everywhere and check it more conveniently :-) If a part of you is being negative, worried, etc. then call their bluff and make fun of them. It's just all about which thoughts YOU want to think/have in charge.

Make your SI "public" in some way for yourself so it's not just your "dirty little secret" http://www.selfinjury.com/ Counter the assumptions that you need it/would feel better for it. Yes, you'd physically feel better for awhile but that's just chemical, like chocolate's effect :-) Do some experimenting; eat a piece of chocolate when you feel like SI :-) or a grape or something totally ridiculous like that to make you smile and relax.