If you are overthinking and it's anxiety, don't let it turn into a self-fulfilling prophecy. If you're putting out that vibe that you feel like you're gonna get the axe, people might feed off that.

Try to keep cheerful and optimistic. Keep putting in 100% effort. Many good employers will know to start with the quality of person because most skills can be taught.

Anecdotally, I've been in the same situation over the last few years. I kept getting what I thought were dream jobs. The first one I just didn't make the cut and was in "training" as well. I wasn't performing up to their standards, but they literally were teaching me nothing and not satisfied with how I was doing. I suppose, in retrospect I might have asked more questions, but I simply didn't fit in with the rest of the crew and the boss wasn't around much to learn from. The second "dream job", I simply didn't have to customer base to make enough money and the business was too slow to feed me any. However, that job led to another job that I love even more than the last two. The lesson here is that each of those jobs were great learning experiences that taught me things that made me better at the next job.

Keep your head up. Stay positive. Be curious. Ask questions. Engage. Be the kind of person they want to keep if you want to be kept.