Every single day we have to make lots of decisions and choices. So what's the best decision you have made in your life till date? Mine was leaving my old job and starting my own business. It was not an easy decision to make but I am glad I did.
I would say, learning online marketing. It is an option that was not there for me in the past, now it is there to help myself financially.
Creating this Universe. While some results are less than completely satisfactory (like war and malnutrition, gaming geeks or Japan), I quite like it, overall. Maybe, I'll create a better one, (version 2.0!), after I scrap this on on Dec. 21.
Great question! I think that my best decisions have been to act ethically in life, be a kind individual, and to try and help others.