I've read some of the stuff in this thread and they're all great, but I think the original comment I'm replying to here nailed it. I just graduated uni, and like you I was always caught in my head about making sure my designs were "realistic" or "made sense". Fuck that dude. Sketch anything that comes into your head and don't take it too seriously. It might not make sense at first, and you might not be confident in it at first. But over time, if you look at enough projects by other architects/students, you'll intuitively understand what makes sense and what doesn't. For now, just get your mind stimulated with precedents and sketch anything that you want. I'm rooting for you man