My old neighbor, Mr. Jenkins, did 100 jumping jacks at dawn like clockwork. I tried to copy that and found that rotating through five basic exercises every day kept me from getting bored. Your mileage may vary, but adding a timer for short circuits changed things up for me. Take this with a grain of salt, but I sometimes pick exercises from a hat to decide the day's routine. In my experience, even simple routines can stay fresh if you tweak small things like your rest time or add a new move once in a while.