I have gone through some times in life where it's been really hard to sleep properly. My kid is three years old now, and he still interrupts my sleep patterns. I'm a teacher, and I never sleep enough during the busy time at the start of each school year. When I'm not sleeping enough, I feel it in my running. My muscles are fine, my cardiovascular system is fine, but something isn't there. I can maintain my mileage, but when I try to push myself, I just come up empty.
The best approach I've ever found to help me get enough sleep, was to get rid of my alarm clock. Not using an alarm clock ensures that I get the most out of the sleep that I do get each night.