Why write? The subject interests me, and I am prepared to do the research to ensure accuracy. However, it's more than just interesst but this answer will suffice for the present. For me, the concept of 'on track' is the intriguing part of the discussion.
It's not so much keeping my writing on track as utilising the opportunities that arise which will enhance the final writing project. I'll give a couple of examples. Writing my mother's story deciding whether it is more akin to the style of a novel or purely factual and I received an invitation to interview my mother for the company Boral. Mamma was their first female accountant in 1949 and the company celebrated its 70th anniversary in 2016. So, to cut a long story short, my article on Mamma was published in December. Straying from writing the story - yes, but that section of her life in the story will be much richer because of the interview for Boral.
The second writing project is of transformation and chronic pain - and what writing style is satisfying to me and engaging for the reader? At a crucial time of decision making (early 2015) I was offered and accepted writing a column in a magazine writing on that very subject! A book perhaps from that??? Stay tuned...
I'll leave you with this parting thought - do you see procrastination, diversions as a hindrance or do you recognise the opportunities that these might create?