Hi, Alicia.
Printing and digital are different media and have to be treated differently.
We usually work big so our work can be printed. When resizing to a web-friendly size the work loses its detail and texture.
So you have to create a web size archive aside.
Once I finish my illustration I paste a flat rendering in a new document. I resize and then apply textures, sharpness filters, or whatever it needed to look great in this new size.
Sometimes, I directly make the copy of the illustration without the textures since I have it all separated in layers, and apply the textures in the new size.
This is a detail of how my final illustration looks at real size:
monster thinking 002 detail.jpg
If I resize I lose a lot of texture as you see:
monster thinking 002 resizing.jpg
So I apply the texture and whatever it needs to the new size:
monster thinking 002s.jpg
It is a technique I learned in photography where you edit a copy for printing and a very different one to look awesome on web. As I said, are different media, the brightness of the screen can't be replicated on paper, for example, so edit your work specifically for the medium is going to be displayed in.
I hope it helps. Have a great day!