How do you stop the constant worry about work when you are on PTO?

I work an entry level finance job. There isn’t enough people to cover my job duties when I’m away. I’m allowed 4 weeks vacation a year. I really haven’t taken even a week’s vacation this year because there is no one to cover it now. I’ve been told by a few friends in similar industries that it’s the company’s problem for not having enough staff to cover. The problem is my company makes it my fault. When we had enough staff I wouldn’t even think twice about work when I was off. Now I worry 24/7, it’s not a good feeling.