Yesterday was one of my two hard day rides a week. I headed south on the back roads in San Martin, switched to the West side of the valley on East Middle Road, then went north for a bit. The hard part is that I try to keep my heart rate up in the “zone 2” range for most of the ride, then at the end, I throw in some sprints. If I do this right I’m pleasantly tired but not overly so afterwards. I got it right yesterday and felt great later in the day.