How do I cope with always being the one who presses people for money?

You can collect from almost anyone, and you are weary, because the role has made you the one who always has to press people for money. That fatigue is real. Being the point of friction, day after day, wears on a person in a way the job description never mentions. It helps to see clearly what this work actually is and is not. You are not taking anything that is not owed. You are keeping promises honest and keeping the business alive so everyone else gets paid too. The unpleasantness people aim at you is rarely about you; it is about their own discomfort at owing. You have simply been standing where that discomfort lands. To carry it longer, protect yourself between the hard moments. Do not replay the difficult calls after they end. Build a small ritual to set the day's friction down, and keep some part of your life where you are not the one asking for anything. You give the business your firmness. Save some gentleness for yourself.