Put together a cohesive to-do list
I tend to have a ton of random notes in my phone with unorganized lists of things I have to remember to do and honestly, these notes just make me forget even more than I would have. Make lists upon lists - the more organized you are the better off you'll be. I think writing things down even in the age of technology is still the best way to remember things and to get things accomplished. Less stress, too!
Set a certain amount of time for things that you can get done - cleaning a room, organizing a drawer, writing a blog post, sending an email, whatever it may be; if you press yourself for time, you'll likely get it done ON time and in enough time to still recover from a not so great day.
Complete smaller tasks
We all have these days and instead of dwelling on the time you lost to get things done, spend the time you do have left in the day to accomplish smaller things. Clean up your desk or do some meal planning - you'll feel better!
Figure out what will make you productive
Instead of stressing out worrying about how much you now have to do, figure out how to get into the zone you need to be in to be super productive. Everyone works differently - for example, my sister studies best with music, while I have to be in silence. Figure out what's going to work best for yourself and set your deadlines.