It is explained really well in this post: https://steemit.com/steemit/@worstdevever/what-are-curation-rewards-and-how-should-i-be-voting
tl;dr - Your voting power goes down every time you vote, but regenerates over time, so if you want to get back to 100%, you just have to hold off on voting for a bit.
Like I said... That's not an easy thing to do...
I guess I'll have to explain in every comment...
@pocketechange
That article is i credibly outdated. The curation system is very different now.