hydrate and sleep well, exercise, find something that interests you to spend your free time on it, dont use anything psychoactive, not even nicotine or alcohol because it might make you feel that "one more bump is okay"
be ready for withdrawals and remember that most of them are psychological.
once you start to get low on adrenaline and serotonin the hard time begins and you have to get through it no matter what.
you can raise a little bit your dopamine levels by consuming good amounts of olive oil.
for serotonin depletion use the 5-HTP supplement, combine the two for best results.
keep track of your blood pressure, it might decrease/increase to harmful levels, to increase if too low eat salt, to decrease if too high eat garlic.
i used mephedrone very excessively on purpose to explore its depths, and i can say it is no big deal to cold turkey it, you just have to take it seriously.
good luck brother/sister, you got this.