Getting a new job is always exciting because it seems like you have achieved one of your career goals, especially if you are hired by the company that you think could provide various development opportunities. However very often a new job means new challenges and difficulties. Many people are not prepared to changes like that and as a result, they want to leave the job soon after they are hired. If you find yourself in a situation where the workload is more challenging than you have expected or experienced before don't make any decisions right away. There are things you could do to make the transition smoother. Also, keep in mind that a more demanding work environment isn't necessarily bad even if it feels like that at the beginning. As a matter of fact, you can learn more and grow into a more qualified specialist.
Don't Quit. Work Hard
First of all, don't try to change the environment as most people are doing. It makes no sense because as you grow professionally the environment will be getting more and more demanding. It is a fact and you can do nothing about it. So instead of struggling with the environment, it is wiser to accept it and change some way how you used to do things at work. It is important to realize that you won't be able to operate on the same basis. When one moves into a new and more demanding work environment the old habits and patterns need to be released. Maybe it was okay to leave at 5 pm at your previous job or there was no problem with reading the latest news during your working hours but most likely those kind of habits are to be dropped. In other words, focus on work and nothing except your responsibilities and established goals.
Another thing that could help you cope with the pressure at work and demanding environment is minimizing the distractions coming from your family or/and friends. If they used to call or text you during your working hours and that was fine before, let them know you cannot afford to do that at a new job. This way you will get much more support rather than distractions. At least it will help you adjust your lifestyle and match the requirements of the position. You can also observe how your colleagues handle stress and their responsibilities. Since you are working in the same company and on the same floor it is likely they are in the same environment. Watch how those people operate - how they organize their time, prioritize their assignments, meetings, projects, etc. You can learn more than you think by looking around.
Lastly, ask for help. There is nothing wrong with that. Most people believe that asking for advice is a sign of weakness but the reality is that only strong people do that. Colleagues (who probably have walked down the same path) understand that it takes time to adjust to the workload. So asking either your direct supervisor or other employees can help you successfully operate in a more demanding environment. The thing is that if you ask them you will receive highly practical recommendations that might change the way you work. No matter what, don't give up before you really try hard. That's how people achieve career success after all.