Dreaming isn't for handling what you've done during the day. Thats what sleep is for. Sleep refreshes your body and re-energizes it so its ready for the next day. Dreaming is just images thrown into our head.

By Lucid Dreaming you aren't inhibiting the brain's work at all. The body is still sleeping, resting and you lose no sleep or energy through it. Your not doing anything physical when Lucid Dreaming, its all mental. Which can actually be helpful as the mind is better awake and aware.

Even if Dreaming was a neccissity, there would still be no harm in Lucid Dreaming as your still not inhibiting it. Why? Because when your Lucid Dreaming, your still dreaming. So the brain still is giving you that dream that you can be aware of.

(Btw, Im tired so I may have worded some of that really bad.)