This isn't a strategy post about how to get paid. (I've taught many a class on this!) This is a pre-strategy post, on how to get your mind right about this kind of situation. Because again: if you're regularly having these problems, you need to change things with your business infrastructure. I'd need to ask you a series of questions about your operations, in order to figure out where you're going wrong.
I'll bet you can't stump me with a client problem. If you're having them, you're probably not communicating your process and your Policies thoroughly and clearly. You also may not be delivering what you promise - or what the client might reasonably expect. You either kept things vague, or you wrote overly-wordy Policies. The former means you left things open to interpretation (and that won't work in your favor). The latter means that since you didn't focus (and write a tight, brief Policies clause) - you encouraged your clients not to focus, either.
In my experience, entrepreneurs who continuously complain about clients (or entrepreneurs who have the same problems with their clients, over and over) usually have some salient issue they are avoiding. Maybe they don't want to do their bookkeeping properly - they're intimidated or suspicious. Maybe they're still trying to prove Mummy or Daddy (or their ex) wrong, instead of turning inward to their OWN needs and impediments. Maybe they want to be Liked - or they want popularity, Followers or clout more than they want to run a sustainable business. Who knows!