Personally, I've never really understood the need to focus on one thing. My trick is to look into the future, pick a few possible outcomes. Work towards them and adapt along the way. I actually find that if I try too much to focus on one thing, I figure out how to exhaust myself with it.

With financial things I've always thought that spending isn't necessary. When I buy something, I always think: "Do I need this? Why am I buying this?". Sometimes it is enough that "I just feel like it now", most of the time "oh well, lets see if I still feel like it in a few weeks".