Advice for succeeding in a more demanding job

Recently I started a new job, which I like. What I do is for the most part pretty easy tasks, but the work is a lot more physical and fast-paced that what I'm used to, and some days I find myself becoming hostile and stressed when I'm falling behind. Going into this position I was hoping it would be a step up from what I did before, and that my new employer might hire more reliable workers than my last one. The job comes with some responsibilities I didn't have before, and it is very team-based at times. The problem is that everyone has to stay on top of all of their tasks to ensure they're not falling behind, because there's little down-time and the process keeps moving on. I've come to realize that the selection of workers is a mixed bag like it is anywhere else. Some are quite nice and informative, and try to be team players. But already I've seen a lot of people standing around talking for several minutes, tons of people don't follow many of the company rules that were discussed in orientation with the exception of days when auditors are watching, and a lot of them seem very out-for-themselves. I just try to stay focused on whatever task I'm on, do it as quickly and well as I can, and also try to resolve issues if I have a free moment and everyone else is busy. I want to hang in there, but I don't want to become a negative problem worker. I don't want to mess up too badly or get angry and cause a scene, or go off on someone. I want to be good enough at what I do. But there's some challenge to it, a process you really have to get down. I realize I'm still new, but some days I feel as though I've been on top of things the best I could be, and there was a very slim margin for error. If you have one person falling behind it can make everything more stressful. Looking for general advice on maintaining positivity and becoming quicker and more efficient in the workplace. Maybe some people can relate to some of these issues and have found things that work for them?