It's a wonderful time to do research, because you don't have to spend all that time working on it. You can look things up quickly, read about it and decide how you will use it on your manuscript. You jot down notes for later. You can check on things that you really aren't sure about. In other words, you can use this time as patching all the holes in the manuscript that you tell yourself you will check on later.
You can also spend your time in bed thinking about your plot and why it is or isn't working. How you can make a character more colorful. How you can dress up a setting to make it irresistible. Sometimes thinking out the plot and reworking it in your mind can deliver the answer to things that have been blocking you from finishing the manuscript.
You can edit what you have already written and fill in places that need more or less.
So just because we are are sick doesn't mean that we are not being productive. It means it gives you some time to really look at your manuscript and work on things that you always feel like putting off until later.
Also, it is a great time to read other works by other authors. Or watch a TV program that you feel is well written and would like to learn from.
Just wanted to share some of the things I tend to do when I'm under par. It also has another positive effect or is that affect on the author, it gets you to thinking of something other than being sick. So sick time can be reflective time for your manuscript. Actually it can be just as productive as your active time.
Don't feel guilty any more about taking your medicine and not writing, because this can be one of the best times for your creative spirit to come out. You can find ways to write a new sentence for one that lacks luster, or research a setting for the next book.
So the next time you are sick, don't feel too bad about not staying at the computer. Allow yourself some thinking time, allow yourself some research time to better clarify your manuscript.
Invent new ideas for tidbits of work that make you feel productive.
And by all means get well.