Good question. I always find this a challenge.
I read a long time ago that we are always giving 100% energy to do everything. That we should only give as much as is necessary.
For example when walking to the bus stop or the car park, we don't have to give our whole self to that walk. Relax and notice how your upper body is trying to push ahead, every muscle is strained to get to the destination. Try spending less energy. In that way you can maintain and distribute the energy throughout the day.
Before going to bed it is a good idea to completely relax in corpse pose (I have written a hub on it). This way you will wake up refreshed instead of feeling tired in the morning.