I have alluded to this concept or flat out stated it in prior blogposts, but I want to consolidate this piece of advice I give entrepreneurs daily (literally, I say the following paragraphs nearly verbatim at least once a day).
Astronomy: The Drake Equation roughly states that (the average rate of star formation per year in our galaxy) x (the fraction of those stars that have planets) x (the fraction of those planets that can support life) x (the fraction that will go on to support life) x (the fraction that will develop into intelligent life) x (the fraction of civilizations that will develop a technology that releases detectable signs of their existence into space) x (the length of time for which such civilizations release detectable signals into space) = the number of civilizations in our galaxy with which communication may be possible (life on other planets).
Summed up: We are dealing with such large numbers of the first variable (stars) that you could take a fraction of a fraction of a fraction of them and you'd still have intelligent communicative life on some other planets in our galaxy.
Startups: You have an idea. Out of the 7 billion people on Earth, you cannot rationally statistically assume that you are the only person with the idea, and that co-invention (especially in information technology) is happening at multiple other locations around the world. Some fraction of those co-inventors have the wherewithal to develop the idea. Some fraction of those are working on it full time. Some fraction of those have funding sufficient to make it successful. Some fraction of those have a veteran staff of raw red meat eaters that have done this before.
Therefore, it doesn't matter how much time, money or experience you have in developing your idea. Someone(s) out there among the seven billion is preparing to take that idea and make it very large. How much time or money you choose to, or are able to, dedicate to growing the business is relevant only to you. The market, and those co-inventors, do not care one bit for your (often self-imposed) limitations.
Summed up: Just because you can only moonlight on your startup doesn't guarantee you any presence in the market. If you can only train 15 minutes a day for the marathon, and someone else is running a 10k a day, guess who is going to prevail. Yep.