You are definitely not done! I'd be willing to bet that it wasn't related to you specifically, but to TIMING.
At a different time, they would have given you the attention you needed with your first job. Everyone knows that even for experienced CNAs, the work is not easy!
The main thing, is you really like the work - that to me, & the fact that you are not too down on yourself, says that you will be good, given time.
When I was beginning, I was so afraid of not being good enough, but over the years, I changed. Occasionally, I have taken a job as a learning experience. Once or twice, I have been "let go" (it sounds better than fired) because I didn't learn fast enough LOL.
Sometimes that adventure (job=learning experience) works, & sometimes it doesn't, & I think it has a lot to do with timing. You will gain more self-confidence with each job, or you might be lucky enough to find a great fit, & stay there a long time.
It's a valuable skill you have, & there is plenty of work!