Ever have a day like this? One minute you're prepping for your next status meeting. The next, an urgent email pops up and you begin replying--and before you can hit send a co-worker alarms you with an instant message demanding your immediate attention to put out a fire.

You notice a few strands of gray that weren't there last month and wonder: How in the world will I get anything done today?

If you're finding it hard to focus and stay productive, you're in good company.

One study by McKinsey found that unnecessary workplace interruptions are costly, with "high-skill knowledge workers spending 28 percent of their workweek managing email."

Another study by University of California, Irvine, found that office workers are interrupted roughly every three minutes and once interrupted--ready for this?--it can take 23 minutes for the worker to return to the original task (more on that below).

If any of this resonates, you need a boost of mental focus to keep you on task. Here are 10 proven productivity hacks to help you.

1. Focus on doing only one thing.

You think multitasking is still a good strategy for success? Research says that's a myth and that multitasking can in fact be damaging to our brains. You end up splitting your focus over many tasks, losing focus, lowering the quality of your work, and taking longer to hit your goals. Mentally focused people are smart enough to work on several smaller chunks to complete a big goal. But they do it by knocking down one thing at a time, then moving on to the next task.

2. Choose the time of day that's best for you.

Some people are super productive and mentally sharp in the early morning. That is clearly not me! Figure out when you are most likely to feel focused (or least likely to feel easily distracted), and block off that time slot for tasks that you know will require your mental toughness.

3. Do this breathing exercise before you start work.

Shawn Achor, Harvard-trained happiness researcher and best-selling author of The Happiness Advantage, tells us to breathe and watch our breath go in and out for two minutes. He says do this every day. This allows your brain to focus on one thing at a time. (Achor says it will "raise accuracy rates, improve levels of happiness, and drop stress levels.")

4. Be conscious of your intentions.

Throughout the day, check in with yourself. When you sense that control may be slipping away, pause, take a breath, and revisit your intention. Take notice of how the quality of your work shifts every hour, as you become more conscious of your intentions.

5. Take frequent breaks.

Brief diversions help, because everyone with a sharp focus will get tired over time. It's exhausting! So make it a habit, after 30 minutes or so, to take a short break before your mind starts to fatigue. It could be as short as a five-minute walk outside to breathe in fresh air and get some sunshine. By doing so, you will reset yourself with new focus.

6. Stop constantly checking your email.

This is a big one. The constant checking of email ritual is one of the quickest ways to damage your productivity. One idea to try out is to avoid checking email until lunchtime. The reasoning here is, if you allow your morning to be focused on your biggest and most important task, instead of focusing on all the problems and distractions you'll encounter over email, you'll have worked much more productively.

7. Speaking of your biggest and most important task, yes, work on that first thing.

Even if nothing else was accomplished at the end of the day, you'll still know it was a pretty productive day. The reason to start out your day with the biggest and most important task is a no-brainer: Your energy level is highest in the morning, and will crash not long after you come back from lunch. So take on that dreaded annual budgeting plan first thing in the morning.

8. Switch tasks.

When you switch between high- and low-focus tasks, it gives your brain a rest after a period of heavy mental focus. Let's take that big important task from No. 7. If you just spent two or three hours in the morning working on it, recharge by taking on a low-focus task, like reorganizing your office, for 30 minutes before going back to your high-focus task.

9. Set three goals for the day.

This is tricky, because you're automatically thinking of daily tasks on your to-do list. But these goals should also include things that will make you a better all-around person, boss, entrepreneur, or (insert your trade). The most successful people I know start the day by putting their mental focus on something that will make them better. What will grow you, give you more energy, make you happier, and set the stage for an epic, productive day?

10. Drink water.

No, I'm dead serious. So many of us (me included, my wife tells me) just don't drink nearly enough water, yet dehydration can cause tiredness and slow things down. Brains without proper fluid can't operate at peak performance. So stay hydrated to keep your focus during the day.