All of the above. I would differ in one thing from MCImes. Practicing remounts at the end of session is good to learn that you can do it tired, and if you exhaust yourself then you haven't ruined your session. That said remounting in the rough at the start of the session can be extremely helpful. Doing a few remounts ups your confidence and reduces fear for all the reasons stated by others. Once you have put your mind in that better place, you will be able to do those turns much better. In addition there is that thing about practice not making perfect; only perfect practice makes perfect. Working those turns in a maximally confident state will increase the chance that you are practicing good habits rather than bad fearful habits when turning. And doing better at turning of course boosts confidence in turning which lead to better turning and so on and so forth.
As far as the issues you are having, you are in a boat that is too tippy. That is ok. I learned in a boat that was too tippy. I would pick a stable ski if i could so it over again and shave a few years off my learning curve, but the past is past. I think you have to recognize that your boat is too tippy and own that fact. In a sufficiently stable ski afterall, the turn would be a non-issue. I have been doing this sport much longer i think than you and have no problem turning elite boats around in the waves. But when i do out and backs in small conditions in my sit on top k1 i almost crap my pants each time i turn it around in the waves. I am mostly ok in the upwind, and a bit shaky in the downwind, but the turn is very anxiety provoking. That boat is clearly way too tippy for me in those conditions. But I accept that and do it on occasion anyway for the challenge, though i never do it far from shore.
You need to get more stable in that ski. I am not sure if practicing turns is the most fun or effective way to do that. What you need is tons of time in the bucket in all sorts of conditions. when balance is better turns will be better. It is very important to paddle in flat and small conditions as well since the stroke goes to crap if you have any balance issues, even if you don't realize it, and you really want to be practicing a good stroke rather than a bad stroke. Again, perfect practice makes perfect.
Just keep paddling and you will keep progressing, but be patient with yourself. It takes a while to take balance to the next level. You can do the work but the brain can only change so fast.
Hopefully something in this is helpful to you.
Zach
Current Skis: Nelo Vanquish AIR, NK 670 double, NK exrcize, Carbonology Feather, Think Jet, Knysna Sonic X
Former Skis: Epic v10g3, Kai Waa Vega, Epic V12 g2, Epic V12 g1, Epic v10 double, Nelo 550 g2, Fenn Elite S, Custom Kayaks Synergy