My wakeup heart rate is still going down

Today is a rest day, but I measured my wakeup heart rate to see if my 7 1/2 hours sleep last night affected the heart rate. The HR was 58. Last week it was 61-62, so it is down a significant amount. I hope it keeps going down, because I not only run better with a lower HR, I do better in my other activities. My "normal" wakeup heart rate is 50-53.