If it is true that “Customer service work can be bad for psychological health…as it typically involves being polite and friendly to customers or clients and having to suppress real feelings and emotions,” then I suggest it must be good for psychological health to have an outlet to vent those real feelings and emotions.
Note: Yes, I know: this post contains something I continuously rant against others doing: misinterpreting and misapplying research data. Also (for the record), I believe being polite and friendly to customers and clients may not be good for ones psychological health, but is does wonders for ones financial health. Bottomline (especially if you work for me and are reading this): being polite and friendly to customers or clients is a good required thing. Take up running to really unvent those suppressed emotions.