My take on this is, often a problem is not itself: the symptom your client displays has a foundational problem elsewhere, which causes them to behave like this

My take on this is, often a problem is not itself: the symptom your client displays has a foundational problem elsewhere, which causes them to behave like this not only towards you but probably with most other people. So first, you need to be aware that it is not you, it is them and let them know it indirectly. How? I read a great advice once that if you "dont react, you will not overreact". The flood gates of pent up emotion will cause severe problems for your business which will lead to outcomes unexpected even by you, and your team. But suppressing negative emotions are proven to cause psychosomatic diseases, which is a boring way to say all this suppressed anger will kill you. What to do? The problem begins to become a problem when you value the emotion more than it is worth. If you think this is making me angry, emotionally you will easily slide into feeling much more anger than is actually warranted. The reason for this is because our built up stresses want a release point, and when you feel angry, those release paths become known to your anger. First, exercise in the morning, intense, fun like basketball and your team, so as to prevent daily stresses to seek release paths. Then when the client starts to get on your nerves, your nerves will handle the client without becoming frazzled or excited. This calm will unnerve your client, and cause them to feel the futility of behaving like that towards you. If it does not make you angry, they will not be likely to behave aggressively because they could wonder: they are so calm! But this would also make them behave even more aggressively sometimes. However, this will all come to an end if you remain calm. In the mean calm time, you can seek clients that are less belligerent and reduce reliance on clients who want to vent it on you. But until then, treat it as a case study in abnormal psychology.