It is a simple Steemit hack. Visit more than 7 days old posts and comments you upvoted. Now start unvoting them to regain your voting power quickly. Do not unvote newer posts or comments as you don’t want to lose curation rewards. Only apply this trick to posts and comments that are more than 7 days old to get back your voting power in shortest period of time.
But it will be really sad if too many Steemians start unvoting old content as those posts will lose their credibility. I would suggest to apply this trick when you need it most.