The goal of successfully managing your energy is to lose less energy over time than you can successfully regenerate. Like your bank account you want what is coming in to outweigh what is flowing out. If you have but one pip of energy, ideally, you want to spend less than 1 Guild Wars Gold in 3 seconds.

However, you can spend more than 1 Guild Wars Gold in 3 seconds because characters have a maximum store of energy. You will not regenerate past that number but you will regenerate up to it.  This means that just with your bank account you can indulge in the occasional deficit spending. You can spend a few hundred dollars on a new TV or a few thousand on a new car even though that is far more than the amount of money you are taking in because, hopefully, you have a bit of money in your bank account to start with. You can not do that indefinitely because eventually you will run out of money, but you can splurge when the need arises. So, a character with a single pip can spend more than 1 Guild Wars Gold every 3 seconds by tapping on the stores of energy they begin with it is just she can not sustain that level of spending.

Eventually, spending more than she can regenerate will result in them running out of energy and being unable to cast at all. What regeneration does when you are sending out more energy than you take in is to put that point off further and further the more pips you add. So, say our one pip character starts with 15 Guild Wars Gold and casts enough a skill that costs 1 Guild Wars Gold every 3 seconds.