That as a cofounder you get constant rejections from literally everyone, including people who won't even use/pay the product that you are building.
For those of you who are cofounders, that must be taking a huge toll on your emotional health, right? How do you deal with these?
The simple truth is you just have to keep trying, for years and years possibly, before something really hits.
Try not to think of them as rejections. Re-frame it as "this person isn't the right user for us right now." That removes the emotional bent from it, and maybe will force you to ask the question of "who IS the right user for us right now, and who's the right user for us tomorrow?"
It’s the equivalent of sore muscles that professional athletes feel after training day after day.