Every time you upvote something, your 24 hour supply of voting power is reduced. I think it drops by 2%. Every 24 hours it regenerates, I think by 20%. So if you want to start off each day at 100% voting power, limit yourself to 10 upvotes per day. On the other hand, new users start at such low reputation and Steem power anyway that you're not really losing anything by upvoting more than that. I mean, each ipvote only counts for a fraction of a penny, right? If you were a "whale," things would be different. Incidentally, you can use this URL to keep track of your voting power: https://steemd.com/@trilo.