“a true tzaddik is like avraham avinu who was pained when he had no guests or like rav aryeh levine who couldn’t say “no” to anyone because he truly loved everyone, and giving gave him the greatest pleasure.”
Surely this was not their natural inborn instincts. They had bechira. They worked on themselves to reach that level. That is our avodah. Mussai ygiu masei limasei avosai. If you feel it will cause burnout and then more worthy recipients will end up losing out, that is a different cheshbon. It sais ki sireh chamor sonachuh rovaitz tachas masao azov tazov imo. Why chamor sonachuh-why not chamor ohavechuh? Because the torah wants us to work on ourselves-to grow.