More than ever we are prisoners of the urgent. We react to what's right in front of us, whether it truly matters or not. Prioritizing requires reflection, reflection requires time. And, well you just don't have the luxury of that now do you? We are so busy trying to keep up that we don't stop to think about much of anything.
Too often we default to "yes." Saying yes to requests feels safer, avoids conflict and takes less time than pausing to decide whether or not the request is truly important.
Many of us have become addicted, unwittingly, to the speed of our lives — the adrenalin high of constant busyness. We mistake activity for productivity, more for better, and we ask ourselves "What's next?" far more often than we do "Why this?" But as Gandhi put it, "A 'no' uttered from the deepest conviction is better than a 'yes' merely uttered to please, or worse, to avoid trouble."
Here are a few tips, so that you can schedule time to figure out how to say no. 
1. Schedule in your calendar anything that feels important but not urgent. If it feels urgent, you're likely going to get it done. If it's something you can put off, you likely will — especially if it's challenging.
2. As your final activity before leaving work set aside time (about 10-15 minutes) to outline your tasks for the next day.
3. When you get in the morning, do the most important thing on your list first. Focus completely on this for 90 minutes, turn your phone off, silence your email. The more focused you are, the more you will accomplish.
4. Take scheduled breaks throughout the day. Working from home I have had to institute this into my schedule even more. I actually started doing simple yoga routines during my breaks to renew myself.