Clients can be challenging, but remember that when they stop calling you with questions or with work to be done, that is the day you no longer have a job. We are here because of our clients, not in spite of them.
Does this mean that the client is always right and that you should take whatever they dish out at you with a smile and a nod? Of course not. No one should ever suffer a client who disrespects them professionally or personally, but an abusive client who must be fired is very different from one who simply asks a lot of questions because they recognize that you are the expert. Yes, clients make poor decisions at times, and some of their questions will seem obvious or silly to you, but your answers and advice are why they hired you in the first place.