You can’t set plans for big goals and follow a dream that is a long stretch. There are so many variables involved, you can’t predict and keep them under control. You can’t be sure how things will pan out in the long run, you can only do some guess work, so the smaller the number the better the chances are of getting it right.

Start with small and have an impact. See if it is really worth something big or the small scale is perfect for the vision. Once you have figured that out, be satisfied with it. You can't live your life stretching something that can no more be stretched, but you can make sure that the length you have gotten to is meaningful and worth remembering. 

There is no harm in aiming big, but you cannot execute big, be open to the possibility of scaling big, but focus your efforts to the present scale. You don’t want to break what you have build or can build to fetch something which is out of reach.