So, I'm not going to rehash the things listed above. There's enough general consensus on those points to be well worth your consideration. Just a couple of thoughts from a fellow IRA pilot nearing completion.
First, I go to great (some might call them ridiculous) lengths in preflight preparation. It means that I'm FAR less likely to be caught off guard by something or have something surprise me. Not that it never happens, just less likely. If you KNOW you are going to shoot an ILS, many airports only have one runway for the ILS and the other runways are RNAV or other types of approach. (Obviously that's a broad brush statement) Look at the IAF for your sector, or the entrance to that IAF and prepare for that before you take off. If you are shooting an RNAV, get destination winds before takeoff so you can plan which runway is likely to be in use, and brief that approach plate before takeoff. Yes, winds can change and you might have to alter that in the air, but the more you can know before you leave, the less stressed out you'll be up there. Sometimes, I go so far as to file my flight plan with the IAF that I anticipate using and then if they want to give me vectors, that's fine, but I've set myself up for success.
Second, as far as readbacks, you may benefit from writing down on a scratch pad just to "trick" your brain into saying the right info. If you have "RWY 34" written on your scratchpad, you'll be less likely to say "Cleared for the ILS runway 32." (or whatever the issue was) Our brains are good at regurgitating information, but even moreso if we reinforce that information auditorily, visually, and kinesthetically (the actual act of writing it down).
Third, and this goes back to your preflight planning. Spend the extra $100 on the next level of foreflight so you can overlay your approach plates on the map. Then you can see your progress on the plate as your make the approach and it gives you more points of reference so you don't mess it up. Then, early in your flight, during cruise, when you know you probably won't hear from ATC for a few minutes, go ahead and load the anticipated approach into your GPS. Yes, they could change it, but if you did all that preflight, you'll have a pretty good chance that they won't.
IFR training is all about being ahead of the airplane. Things in the airplane CAN happen very fast, especially in higher density airspace. CHEAT! Get a head start on the airplane, and it will have a harder time catching up with you, much less getting ahead of you.
So I'll give you an example. Tomorrow, I'm flying KIPT-KBGM-KAVP-KELM-KIPT. Should build about 3-3.5 hrs of IFR XC time and shoot approaches at 4 airports. At work tonight, I will print off the 4 approaches I have requested and highlight them and brief them to myself. I will overlay the plate for Binghamton before takeoff and brief it before we leave. (Also brief ODP etc). I know my IAFs for each approach I plan to use (2 ILS and 2 RNAV). I may even load the anticipated approach in the 430 before takeoff. En route, during that ATC quiet time, I will brief my passenger (in this case, my instructor) on DA/MDA, Stepdowns, glideslope intercept points, missed procedures, etc. Finally, if something DOES change, ATC assigns you a different approach runway or something like that, get on the heading, and then get everything changed over as soon as possible. That keeps you from getting lost in the weeds.
Like
@Mxfarm said, IFR is much more about your task organization than about the actual flying, but the flying will suffer if you don't handle the tasks appropriately. Best of luck to you and feel free to reach out via PM if you need specific advice. I'm not the guru, or anything like that, but I'm going through it too.
I think you're being too hard on yourself. It's ok for this to take a while, and the fact that you're aware of the mistakes means you'll sort it out. I think part of it is what someone above posted, that you're really learning about 3-4 things at once, so it's natural that you're really only going to get better at one at a time, and even that progress is going to be up and down. All of this is far better than someone that rote memorizes all of the procedures and flying, and when they get behind in real life they freeze up and don't know what to do. The longer road may be a PITA, but better in the long run in my view.
Every 30k hour pilot was once in both of ours shoes, and any instructor worth anything will take zero offense at your wanting to work with another instructor if there is a mismatch between you.
