I personally think its unprofessional to send clients texts to drum up business but that's me, I imagine my clients would be horrified to have me text them full stop.
On it being quiet I'm a daytime worker and I'll happily call it a day if my phone isn't ringing or a booking lined up by 1pm, we all know we can be dead as the grave one day then flavour of the month the next, as Scarlett O'Hara famously said "After all...Tomorrow is another day" is my mantra when its quiet.