If someone is negative and you care for them, take some distance. Possibly communicate to them what their negativity is doing, if this is feasible (some people can't hear it :o). If you don't particularly care for them, then distance yourself completely.
Follow us positive folks around for a while
Move as far away as possible or relocate,change is sometimes good.
I'd put on my headphones and listen to music, it calms me.
maybe we can't help it