Like every other Mida, you start with conscious efforts and that leads to subconscious and automatic behavior. Once you understand, logically, that there is no need to rush the matter and that it won’t help, tell that to yourself — almost audibly — and act accordingly (e.g. breathe slowly, tell the person that you can wait, relax in your chair, smile).
Once you fulfill in your actions what you know in the intellect it becomes more a part of you. The more you do that the more it becomes ingrained. Eventually it will become part of your nature.
You’ll get there sooner than you think. Be patient!