I prioritize, I work on one thing at the time and all the things at the same time. I know it sounds a bit confusing, but it's how your body works finally, you're able to breath and walk and give a hand at the same time, right? So why not answering the phone, looking at your email and nodding to answer someone at the same time; or answering an email from project A, being sure your team is on track on project B and already thinking of your postmortem of project C. Of course you cannot do everything at the same time all the time. But you see my point, right? You prioritize your projects, your tasks.
And when I feel a bit overwhelmed (yes, it could happen), I remind myself that I just do some digital marketing. Basically, I help to sell some stuff thanks to the web. I DON'T SAVE LIVES!
Because, it' important to be able to distinguish what is important to do right now and what could wait. That's what I expect from my teams, being able to balance their actions in order to have better results. Once, you balance your projects and professional tasks, you begin to be more balanced and peaceful at work as well and so you work better.
It doesn't mean that you work less, no, it means that you put your energy at the right place at the right moment, it's the contrary of being all over the place for a very poor result.
That's the ultimate secret, you're not working on an open-heart surgery, you just sell some stuff. So, breath in, breath out, prioritize and go back to work!