The most significant aspect of training

While I was running, I was thinking about training and about what single factor would be the most important to a person training to run. I came up with sufficient sleep at night being my most important task. If I don't get enough sleep, my energy level plummets. I expect that younger people might not be affected so much by lack of sleep, but I'm really affected that way. Also important to my training is listening to my body and adjusting my training accordingly.