If you assume that your energy capacity is roughly constant, then the only way to have more energy after work, is to spend less energy at work.

Some people subscribe to the idea that you can generate more energy through discipline or enthusiasm. In my experience, it's like dipping into your reserve tank. It works in short bursts but actually requires more effort to replenish (see burnout).

The older I get the more I'm starting to resent this idea of "being productive". Lions sleep 3/4 of the day, are they productive? Something something about the nature of play and learning in kids and this relentless focus on being productive..