I believe that routine in general helps a ton. Go to sleep at the same time, eat at the same time, go for a walk at the same time, etc. You will wake up at the same time as a side effect. At least that's what happened to me during covid, when there were no obligations outside of working hours. During normal times, I will stay up late one or two days a week for social events or have to get up early for travel. That messes with your rhythm, almost like being jet lagged.