If you're going to practice Aikido there will be lots of decision points where you can opt out. There will be lots of reasons to decide to stop coming to class. One of mine was in front of me right from the beginning. I was afraid of falling, afraid of rolling, and very afraid of sutemis.
I had to face that fear. Explore it. There was no magic moment when I overcame it. I am still working on my ukemi. It's better but it's still not natural and smooth. It may never be.
I simply decided that it was not going to be an excuse to quit.