I got an invite to write a book in 2014. Initially i thought it was very easy and can complete within 3 months. By this assumption, i agreed and start writting. When I start writting, i understood that, it is not easy at all. As a first time author, i was litterally struggling. The only factor that pushed me was, I already spent months for this, so If leave the project, I will lose that months. So I kept going.
After 1.5 years, my first book poped up and it was well recieved. Immediately after that, I got the next invitation to write second book. The thing is, the book subject was very good. So I agreed again by understanding all the cons of writting. I have spent 6 full months (full time for completing the next book. And I am keep on getting invitation and because of the experience of first book, I could easily draft the other books. It was a tough time for me too. Only less income, but only motivation was, I am doing something challenging and I am learning lot of stuff, also I am writting about the technology I like the most.
These factor pushing me for writting me again :)
Sorry for the typo and grammatical errors. :)