2. I stand up at least once an hour and walk away from my computer.
Maybe you have a fitness tracker that reminds you when you've been sedentary too long (typically once per hour, at least on my Apple Watch). If not, you can set your own timer on your phone or even online to remind you to stand up and get your blood flowing again at regular intervals. This is not only good for your body but also your brain.
I find that when I stand up at least once per hour, I can sort of shake off the haze that comes over me when I'm focused on one task for a long time. When I sit back down, I feel refreshed and ready to get back to it. Bonus tip: the better hydrated you are, the more often you'll have to get up and use the bathroom, so that might be helpful here too.
3. I lock myself out of social media during periods of heavy workload.
Social media is a time suck during my free time — I can't afford to have it ruining my work hours too. While it's fine to take a little break now and then to browse the web, I try to ensure I'm using that time wisely, say, to catch up on the local news or look up a recipe to make for dinner that night. I know if I get on Twitter or Facebook, I can kiss goodbye to valuable time.
I now have enough self-control to just avoid going to those sites while I'm trying to accomplish a particularly large or pressing task, but if you don't, you could always use a plugin or website to do it for you. I recommend the Google Chrome add-on StayFocused to keep you on task.
4. I create my own business hours, if possible.
Whether or not you can actually do this depends on your profession, your company's policies, and how timely your work is. The standard 9-to-5 isn't for everyone and if you're working on projects that don't adhere to those hours, there's no reason you should have to either.
Maybe you're a morning person and love getting up at 6 a.m. and cracking on with the day's tasks bright and early. Or, maybe you're a night owl who works best in the later hours of the day. I'm the former and thankfully, my boss doesn't seem to mind. As long as my work's done that day, it doesn't matter what time it happens. If you can swing this, it will make you way more productive.
5. I work ahead instead of playing catch-up.
When I've finished a given day's tasks, I don't simply close up shop even if I'd prefer to lounge in front of the TV. Instead, I look into the week ahead and see what else I have coming up and if I can make a dent in the workload starting now. Doing so means I have much more wiggle room if things come up the next day or later that week and I don't get too behind.
Again, this isn't possible for all jobs, but if it is for you, I highly recommend it. It's way better than getting stressed when you fall behind later down the line.