We always tend to look at things in a more fearful/negative light when under stress. The key is not to focus on the stress, but on the task at hand which for you right now is doing your best in the training process. Once you are successful through that, you will probably find your outlook will improve significantly, allowing you to make a more reasoned (instead of stress chemical induced) decision. Your feelings don't always tell you the truth.
Forget the naysayers and whiners on Internet forums. It would seem the majority of them trudge on wherever they are and do not quit. Apparently it is not bad enough for them to quit, so why you? Don't let their choices affect your life's course.
Are there some parts to the job that are difficult? Absolutely, but that's the same with ANY job. You just have to choose which parts you are ok with being difficult and which ones are not acceptable to you....again it is a choice. I recommend against making that choice right now though, wait a while and see what happens.