Do you know how many rolls of film I f***ed up when I started? Calculators don't count that high!
The quick answer is that using several cameras and doing things different ways introduces more variables into the system. When you are learning, you want to keep things as simple as possible until you understand how everything works.
I know it's discouraging when mistakes keep happening but this is the time to keep going, not the time to quit. The frustration is part of the learning process. Stop now and you won't learn anything. Everything you have done will be for nothing. In business, that's what's called a "sunk cost."
Keep it up! You'll get the hang of it!
As Thomas Edison said, "I have not failed. I have just found 1,000 ways that don't work."