It's important when repelling negative energy to not forget the basic physical things; are you eating correctly, getting enough sleep & exercise and keeping hydrated? Even one of those being neglected will cause you to feel negative energy within yourself, so remember to watch out for overheads.
Besides that, also remember to sort out any sources of negativity you can, externally. If you're hanging around with people who cause you to feel negative, consider backing out of that group and either finding people you enjoy being around, or practise being alone for a while. If there's fights that keep recurring, try sorting them out with a fresh perspective. Create your own peace.
Finally, with regards spells, the best negativity cleanser I know of is to let a black candle burn all the way down. It helps if you anoint it with a good cleansing oil and visualise all your negativity being absorbed into it, and then burning away as the wax does. If you've any left in the dish afterwards, I always burn that bit in the fire and make sure it's good and gone.