Sesh safty

Hey guys, I've been wondering about the effect of coke and ket on serotonin levels for depressed or sensitive persons.
I stopped taking md and xtc a year ago because it was too hard on me, for 5 days after I was very sensitive and started crying for random stupid criticisms etc. I would like to reduce at maximum all that shit anyway cause I know it's not great but it's hard to resist and also the occasional banter is quite enjoyable.
I started taking k because I didn't have that effect on serotonin, or at least I didn't felt it at first (it's been about 9 month k is my drug of choice, with occasionally some c to go along or speed).
This week end was at a party did c & k, been feeling down ever since, sensitive etc, nothing comparable to xtc before but still I can tell it's hard on my brain. Was wondering if it's because of the c or k or both, and what people in my situation have done in the past not to feel like this (heard about 5htp, although would rather not take any stuff to put extra stress on my liver and kidneys or whatever).
Is the only solution is stopping everything or making it super super super occasional ?
thx