There are only so many hours in one day.
Yet some people seem to pack a lot more into 24 hours than others.
CNBC asked successful entrepreneurs and CEOs how they manage overwhelming to-do lists and overflowing inboxes — and ultimately, how they get so much done.
Here are their top productivity tricks:
"I get up in the morning and I'll make a list of the five things I want to get done that day — and without exception, I have to get those five things done. If I end up getting some things in addition to that done, great, but I always have my knockout list," says the entrepreneur and star of CNBC's "The Profit."
"I just physically write it down. I have little cards in my closet in my basement. They're long, narrow cards, with my name on top — and they make really cool paper airplanes, so when I'm done with them at the end of the day, I like to make paper airplanes out of them."
"Calendar management is the single most important thing, especially as you get busy and have more responsibilities," says the CEO of JPMorgan Asset Management.
"You have to be maniacally focused on owning your calendar — on having the lists of what you need from other people and what other people need from you. What are the short-term issues that need to be dealt with? What are the long-term issues?
"Unless you can stay on top of that religiously, it will end up owning you, and that's not a way to go about staying organized and being on top of things."
"I'm always trying to maximize my time," says the "Shark Tank" investor and founder of FUBU. "For example, I'll do my emails when I'm on a plane, instead of when I'm in the office. I try to have my team members handle as much of the meetings as possible — I'll be involved in the last part so I don't have to sit through five separate meetings of the same purpose. And when I have personal interaction, I try to maximize that as well."
"I have a lot of little notebooks," says the celebrity trainer and fitness entrepreneur. "I do a lot of little notes and ideas, and then I figure out which ones I'm going to keep, which ones I'm going to save for later, and how I'm going to craft the bigger piece out of many of them. I grew up as a chess player, so I think that's part of it — I need to see all of the pieces or the obstacles and then I'll figure it out for myself.
"I like the notebook so that I don't leave things behind, because I do run fast. I get so many emails and so many texts that sometimes it's just easier for me to brain dump there."
"I think the two least considered small words in the English language may be 'over' and 'next,'" says the television writer and producer. "When something is over, [it's] over. We're onto next. I live in that moment. I mean this is it — this is the best conversation I could possibly be having, and it took me 93 years to get here."
"Like many other CEOs, I use my inbox as my to-do list. I don't let myself go to sleep unless all of my to-do's are done, which means that my inbox is empty," says the co-founder and CEO of WayUp. "If something isn't urgent, I use the Boomerang extension for Gmail to make sure that I send non-urgent things to be returned to my inbox the next day or week."
"It's very easy to get distracted by your inbox or phone. When I have a big project or when I need to get something done — and done well — I shut down my email, I turn off my phone, and I put on some of my favorite music," says the co-founder of Noosa Yoghurt. "I just dig in and get it done."
"I've enjoyed 'gamifying' my to-do list," says the co-founder and CEO of SeatGeek. "I have an estimated number of minutes for all tasks and have written software to record when I begin and end each item. Each day, I challenge myself to hit an efficiency goal: number of actual minutes divided by expected minutes. The best part of playing a game by myself is that I have every spot on the leader board."
"When it comes to productivity, I'm a huge believer in a good old-fashioned list. I love being able to cross things off as they're completed, and it's a reminder right in front of me when something has to get done," says the co-founder and head of product of SevenRooms.
"I also block time off in my calendar to make sure I can focus on outstanding projects. My new favorite trick is to set alerts on my Apple watch, as well as Slackbot reminders. It's a quick digital reminder that really helps when you're wrapped up in something else."
"Plan your work and work your plan," says the co-founder and CEO of OfferUp. "I make sure to prioritize alone-time on Sundays to focus on the team's top priorities for OfferUp across each department. I then spend the week supporting the team to execute on these priorities."
"I evaluate how long it will take to respond to an email," says the CEO of Trust Science. "Those that take under two minutes, I will respond to right away and clear out first. Those that will take under 10 minutes, I do next — I batch them, meaning I'll respond to them two to three times per day. Those that will take longer, I will respond right away and indicate that it may be a day or two before I can get back to them.
"This way, everyone gets a response within 24 hours and expectations are set properly. This approach keeps the emails at under 10 per day. Not having a lengthy inbox keeps me productive and stress-free — and more importantly, those counting on me also get timely responses, which increases overall productivity."