Design should go unnoticed. As a designer, you know you've done a good job when users don't have to think about the work you did as a designer. For me, I find my inspiration during my moments of mindfulness. I look closely at the objects around me (my lamp's on-switch, the shape of my computer mouse, the lid of my water bottle, etc.) and I think about how I interact with them. What about them makes them "good" or "effective" products?