If you're happiest when your day is planned out, with lists of things to do, and a tightly-packed schedule, then you like living a structured life. When something is structured, it's arranged according to a specific plan.
Structured is an adjective that comes from the noun structure, which is something that's been built or put together — usually, we think of a building being a structure. Anything that has been put together in an organized, deliberate way can be described as structured. Clothing designers sometimes call certain garments structured when they are carefully tailored and deliberately shaped (like a blazer), rather than loose and flowing (like a long, unfitted skirt).