ahahah wish I knew the answer too but it's really about pushing yourself. I haven't written anything on hubpages in months till just about 8-9 days ago I was like no Karishma you have to write.And that's it I wrote a 1200+ words hub and I felt so good after writing it I ended up writing another 1400+ hub last night.
It's all about pushing yourself a bit then it will follow. What you can do is try to narrow down on a topic and start with researching. Once you have researched you will automatically be motivated to write a good hub. Remember quality is better than quantity. Add relevant links, pictures, videos and polls.