Firstly, have an eye test and make sure you're using the right prescription spectacles for computer work. I find a laptop easier to use than a PC, it's a better distance for me to read. Try adjusting the brightness to see if that makes a difference.
Many people have short attention spans, it's one of the things which makes online writing a challenge. If you lose interest in the hub, you can move on. There are many styles of writing on HubPages. I'm sure if you found one that suits you, you will want to carry on reading.