There's not a good way to come down - water can help the kidneys and liver process drugs, but the process can only be facilitated so much. Maybe a detox tea would increase filtration slightly? (Milk thistle/dandelion kind of thing.)

Time is the only way to come down from ANY drug, including THC.

But the best way to act normal and function normally is to hydrate yourself, eat a good meal, and stop freaking out. Keep it under control and do all the things you'd normally do to function well.