In an day it is perfectly natural after a lot of exertion, physical or mental, to have your energy level drop. You started the question with what I see as the right idea "energy management" but I also see possible concern with the ending of "quickly restore."
How do we manage our energy? I think it's very much in line with GTD. We need to look at it as a project. Steps must be taken. Things may need to change. Maybe we need to change our exceptions? Maybe, just maybe, you won't have energy at that time of the day. Could you modify your schedule to be active at home in the morning? Or, do you have a schedule where you could leave work, do things at home and then go back to work? Weekends might be the only time you could fully commit to those interest.
I am a morning person. I wasn't always. Now, I like to get up around 5am and start my day. Some mornings I putter around the house. Some mornings I play guitar. But, I know the morning is when I will do most of my things. At the end of the day I am tired and like to take it easy. No thinking, no mowing the lawn. That is not a part of my current natural cycle.
Of course coffee works wonders too. (but if you're like me, coffee in the afternoon means no sleep...and that is a larger problem!)
iPad, iPhone, MacBook, PC; all running Nirvana, iCalendar and GMail
Mastering Workflow (2012 & 2013)