Thanks! The way I try to scope my own games is by making the smallest possible version first, and then adding more features or content afterwards if I still have the energy to do it. I started Ducky's Delivery Service by making a smaller version with a few levels and no story first, and then I added those later. My last game Chessplosion didn't have an adventure mode or online multiplayer until I had finished making the rest of the game.
So if I get to the end of making the small version and it took way more time than I expected, I have the option of releasing a small game instead of being stuck with half of a huge game that I don't want to finish. I ended up finishing the larger versions of Chessplosion and Ducky's Delivery Service, but I'm glad I made them this way! Maybe I'll get better at estimating the scope of large games in the future, but this way works fine for now.