A piece of advice I have for you is to never get too attached to a firm. Last application cycle, I went into it with the mindset of applying to firms that I really wanted to work at and that I built some sort of inner connection with. After receiving more than a dozen pfos, I found myself in a slump. However, taking a break and changing my mindset to 'apply to any firm you find interesting' rather than 'the firms you have chemistry with' was definitely the turning point in allowing me to gain some success.
Take a break, don't get emotionally attached to these firms that are sifting through thousands of applications, and you'll find that each rejection turns into a 'meh' rather than an 'ouch'. You kind of need to be robotic and indifferent so that you don't find yourself in a slump!