Why do I aim too high ?

well its kinda complicated to explain but I will try.
every time when I looking for idea for a game I aim too high with my idea.
its like my last idea was to create a hack and slash like DMC game with smart ai, cell shading, rigid body and a lot of other stuff.
the problem is that I don’t know how to do half of this… it took my few days just to find out how to make cell shading…
so I said to my self well maybe I will just create a 2d platformer but then I was like “I don’t know how to draw >_<”.
any way wanted to hear what would you do in such situation ?