One of the best ways to become immune to anything is by exposing yourself to it. An actual strategy of exposing yourself to a stressor is called a micro-exposure strategy. therapists use micro exposures to combat phobias. However, you can use micro exposure as a strategy in door-knocking to get comfortable with basing rejections at the door. This will really help you win your game. Here's how micro exposures work. It is similar to how hikers at high altitudes gradually ascend, they ascend a short section then they pause they can't reach the top with a direct sprint. If they did this, they'd suffer seriously and need to retreat completely step by step and level by level their body must adjust to the high altitude slowly but surely they break through the altitude barrier, it actually isn't a barrier at all. They just needed to gradually adjust to it. It didn't hold them back from ascending the mountain and reaching the peak. You can treat facing uncomfortable situations and real estate the same way. Just as hikers gradually reached the top breathing freely, you will become strong and unaffected when facing a no what used to be very uncomfortable eventually becoming another door on your way to achieving your goal. The bottom line is that your exposure can build up your natural immunity and strength.