Different Approaches to Memorising Music

I have been away from the piano for several weeks. Today I sat down and played Dr. Gradus without the score. I got through it, but with a few mix ups. It seems that to really have a piece memorized, you have to have worked through it from many different approaches. It is very different to playing a piece through without the score after practicing it for a half hour, than playing it for the first time in several weeks! There are places that I forget how the music sounds, others where I forget specific notes, and others where I need to memorize the chords. I am back to daily practicing, will log my progress here.