Is guilt a waste of time?

I just finished reading something on the internet about guilt being a waste of time and energy. They are not saying that a person should never feel guilty if they did something wrong but that you should just more or less chuck it up to experience on what not to ever do again.
The idea is that guilt keeps us from feeling peaceful and is more harmful than good.
I was thinking this may be true but then I remembered that children and pets may feel guilty for a while and then forget what they did wrong and will do it again.
So I started to wonder if perhaps guilt has a purpose. Maybe it is the one thing that seperates us from animals.
It may be not so good for us because it can add stress to our lives but overall it helps society as a whole, because we realize in time that we do not want to build up the guilt and that keeps us in check.
I mean if we could all discard guilt so easily, would we really care about guilt as a consequence?