I tend to keep a note file open on my phone of cool things I'd like to have. Then, I go through that list and think: can I build this? I make sure not to consider whether I can buy it straight-up right away—sometimes it's more fun to build the thing you want instead of just buying it, and about 90% of the time, you end up being able to build a project that suits you instead of making do with a store-bought item that doesn't quite do everything you need.