You don't need focus; you need to understand what your goal is. If you're dropping projects that look "unfinished" because, in reality, you've gotten what you want from them, that is fine. It only looks sloppy from the outside.

If you're dropping projects before you get what you want from them, introspect on why. What's happening that leads you away? Address that.

I recommend reading Barbara Sher's "Refuse to Choose"; it provides some useful tools for people who like to do 70 different things, including how to have lots of ideas without having to act on every one immediately.