some people were asking me some questions, so just wanted to share since others going through the process would likely have the same questions:
yeah, it can be scary at the time. and then i look back, and see, it wasn't as bad as i thought. after switching the first time, it was way less scary to switch the second time, since i knew it was possible.
Without searching for it specifically, I have met 5 other people who switched into psych. And, to get my PGY 2 spot in psych, that meant someone switched out of psych (for that resident, it was to neurology). At the time, I felt like I was the only one going through it, but in reality, there is movement between specialties. i believe some programs have pgy2 spots open, anticipating people will switch into psych.
in regards to going through ERAS for my PGY1 spot, for LOR, i had my PD write a letter (stating i was a good resident, wasn't switching because i was a failure), the psych clerkship director for my MS3 rotation, and then i was able to squeeze in a psych rotation in my TY that month, and had a letter. TY internships are often flexible, so i was fortunate to make a last minute switch into that elective rotation-- if you can schedule a month, or some time, that would be helpful for you. One person who switched into psych didn't immediately make the switch (did the intern year, took some time off, got psych experience that year, and was accepted the following year). I couldn't have imagined taking a year off to figure it out, but something to think about.
in regards to the personal statement, i just said what was true to me: I liked both rotations (my original chosen specialty, and psychiatry). the timeline to choose was quick, and i realized i chosen wrong. and these are the things i like about psychiatry. at the time, i thought maybe i had to write a PS that was really going to prove something. but, in retrospect, it seemed mostly like i had that attitude because i was trying to prove it to myself. in interviews, nobody questioned why i was making the change. and, after 4 years of going through personal statements for applicant after applicant as a resident... most people seem not to care about PS significantly anyways (my experience, maybe different elsewhere).
in regards to my interviews -- i was very specific with what i was trying to accomplish. my psych clerkship director had mentored me in the process (he had switched from neuro to psych, so he was a good resource). he told me he would rank me number one, if i made the switch. and i believed him. so i had that interview with that program, and it was my backup. my real goal though, was trying to get to a specific location, and there was only residency in that location. so i hit that residency hard. and they accepted me. i was offered other interviews in ERAS, even that late, but as I had a specific goal, i only went on two interviews, knowing that i for sure would have a spot.
after doing a psych intern year in that location, i wanted out of that location. the reason i was there no longer existed (had nothing to do with residency). again, this was late, and after the match had already occurred, that i wanted to make the switch. since it was after the match, some programs knew they were having some PGY2 openings (from other residents who were switching), so i looked through resident swap, and the APA clearing house. It is much less formal when doing it out of the match. I just sent an email explaining my situation, my previous LOR, my previous personal statement, pretty much unchanged. I made some contacts, focused on one program. It was so late that they had already completed their in person interviews. We did a phone interview only (not even like factime or skype). They accepted me a couple days later, so I had no need to do any other interviews. the residency program i was leaving filled that spot within a month.