(Some) Clients might not like to hear that you are human.  The best clients would understand the pressure we are under and would understand should you say something like "This is an issue that deserves more attention than I have. Would you mind if I extended your return?"  or "I have so much work piled up. Can you help me and research this or give me more information about this air conditioning systems?"

I try (try!) to bring some humanity - to both sides. They aren't perfect and deserve sympathy for not providing everything we need when we want it. We are human and can't provide everything clients need when they want it.

I recall a brilliant and hardworking CPA begging - literally - a client to not make her do the work he wanted.  She couldn't treat herself with respect. And her client saw her as a robot, a machine worker that he needed to get something done.