Most of this is due to my day job(full time job). And so lack of motivation or loosing interest was because of the less time I could devote to it.But I still do not agree on :
"a lack of commitment to one thing is just as productive as doing nothing at all."
When you work on side projects you learn new things or you practice old things which makes you perfect. So keep doing something is always better than nothing. Because of these unfinished side projects I was able to learn python, machine learning, data mining, django and so many other tools and technologies which I would have never learned as these are not related to my day job(all java).
So I would still vote for keep doing side projects whether or not you finish it you have something learned in the process.