Alan,
Congratulations on your graduation from picture taker to budding photographer. Before anyone goes crazy, I am not speaking strictly of your use of manual mode, but of you beginning understanding of the relationship between light, aperture, shutter speed & ISO. While manual mode obviously makes you think of all of those, so does the use of the Aperture and Shutter value settings. They all have their uses, their advantages and disadvantages and learning them will come with time.
It is always good to see someone go from the "I just let the camera do everything in Auto Mode and usually get nice pictures" to knowing how it all works together and being able to recognize the problem areas in any given situation and correct for them. So enjoy the ride, it can be fun one.