ccpsych

To add to the point folks have made about making sure you really want it, I will say that two rounds of applications have taught me that it's definitely okay and probably even a benefit to take time off after you graduate and really think about what you want to do. 
Finishing my undergraduate thesis was so stressful and I can't imagine how I would have survived if I was applying at the same time. I first applied in the first round after I graduated and I was still so exhausted and jaded and just was not excited about the prospect of going back to school. Even though I didn't feel good about it, I submitted applications because I thought it was what I was supposed to be doing, but I didn't put my best effort in and didn't apply for funding and was unsurprised when I got all rejections. It was demoralizing and a huge waste of my time and money.
But, taking a second year off allowed me to rest and have some free time again. I was also able to keep working on some research from undergrad and eventually get them published and present at conferences, which were huge strengths on this round of applications. I also got a good job at a nonprofit on a contract, so I've been able to save and prepare for moving to my new school and I had experience in a professional environment which many fresh undergrads don't have. By the second round I was ready to go to school and found myself distracted at work thinking about research! Taking some time off can allow you to present yourself as more mature and committed to the program.
Also, apply to as many (relevant) schools as you have energy for and can afford. I only applied to three because I was also working full time while preparing applications, but it became clear pretty quickly that all my hopes were riding on one school. That's a super stressful position to be in (I was accepted thankfully), and I didn't realize how much the process came down to luck and how much I had stacked the odds against me. I wish I had applied to a few more schools and maybe branched out a little bit from my specific topic of interest.

Like many others in this thread, I have applied 3 times. I was completely unprepared the first time; I got 4 interviews the 2nd time, but was rejected from all; and I have been accepted this 3rd time, and to my top choice of programs. I've also learned a lot from this process, some of which I think is worth sharing:
Stop focusing on everyone else around you. I made the mistake of always comparing myself to both other applicants and students, and I always felt a sense of inadequacy. Even at the interviews, I always felt like I was the weakest candidate there and had no chance. Even during this current cycle, those thought persisted. For example: the program that accepted me interviewed 8-10 applicants per PI, so there were a LOT of people there. I thought for sure, I had no chance. Well folks - I got in! That goes to show that you have just as much a chance as anyone else at that interview. And, in general, you have no idea how well someone is going to mesh with a PI or program, so don't compare yourself to someone who you feel is superior.
Take your time. If you feel any sense of uncertainty, I would recommend taking a year or two off and working in a research setting. I was rejected after applying straight out of undergrad, and again the next year. I actually did not apply last cycle, due to a job commitment. However, I am very thankful for the experience I was able to gain in these 3 years I will have as a research assistant. I feel much more prepared for graduate school, and that definitely came across on my interviews. I have absolutely no doubt that this is what I want to do.
Prepare, but don't memorize. It is very important to practice answering some questions that may be thrown at you, to avoid looking like a "deer in headlights" during the actual interview. Topics like your research interests, potential study ideas, your past research experience (things you learned), and "why their program" are all pretty standard, and they expect you to be able to answer them with ease. However, you don't want it to come across like you've memorized a canned answer. The more natural your conversation flows, the more comfortable you feel, and the better rapport you have. Just be yourself - you know your stuff!
Don't give up! If this wasn't your time, it wasn't your time. Don't give up just yet. Of course, there may come a point where you at least consider another option, but give it a little time first. This process is grueling and competitive, and honestly, timing and luck definitely play a part, as well. You may be the most qualified candidate out there, but there was just someone else who meshed better with your POI. It was just the wrong place at the wrong time. Just remember to pick yourself back up, take a deep breath, and take another go at it. Mentally, physically, and financially, it's tough - but it's also an amazing learning experience. THis is weird to say...but I'm almost glad I was rejected so many times. The program I was accepted to was my top choice (I had never applied in the past), and I couldn't be happier. I am so much happier with this acceptance than I would have been with any of the other I interviewed at. 
 
Congratulations on all who were accepted, and best of luck to those who continue their application journeys. 

I'm new to psychology as a profession. With previous grad school applications, when I was on a watilist, it was perfectly acceptable to ask for updates about status and, often, schools would offer updates without me asking. From what people are saying here, this seems like it's different in psychology. As I'm sure you all can sympathize with, I'm getting really anxious as April 15th approaches. I would love to get an update on my chances, but that seem uncouth in this field. So, 1. am I right? 2. who else is currently at the mercy of one or more waitlists?

Just got accepted off the waitlist for my dream school ?. Alternate for CGS-M but hopefully good news will come soon for that. 

I'm in the exact same situation as you, except the schools I applied to apparently don't do interviews. I've seen people post rejections and (two) acceptances. I still haven't heard anything and my application status is "under review." It's driving me crazy but I'm too nervous to reach out to the programs to find out where I'm at! Good luck!